# 500w Halogen Exposure Unit



## scrible1980 (Feb 21, 2008)

Hi,
I have just built an exposure unit that has a 500w halogen bulb sitting approximately 40 inches away from the glass screen. The 500w bulb is only temporary until i get my 1000w metal halide wired up and ready to go. I use dual cure emulsion and was wondering how long it would take for me to expose using the 500w bulbs? A friend of mine has a similar setup and i'm sure he said that he can get screens exposed in 12 mins - does this sound right? Just thought i'd ask cause i don't want to go wasting emulsion!
Thanks.


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## denck (Apr 7, 2009)

I would start out at 5 min
My homemade unit has 4 500 wat halegen lights and my burn time is 4 min


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## RichardGreaves (Nov 7, 2006)

*Re: 500w Halogen Exposure Unit at 40 inches*



scrible1980 said:


> The 500w bulb is only temporary until i get my 1000w metal halide wired up and ready to go. I use dual cure emulsion and was wondering how long it would take for me to expose using the 500w bulbs? A friend of mine has a similar setup and i'm sure he said that he can get screens exposed in 12 mins - does this sound right? Just thought i'd ask cause i don't want to go wasting emulsion!
> Thanks.


You didn't share the name of your emulsion and almost every dual cure has a different speed, so exposure time is hard to predict.

40" would be the distance if you want to cover a 25" area, evenly.

*MIDWASTE* has told us he exposes with a 500 watt halogen with safety glass removed for 12 minutes at 20 inches and gets a solid step 7 on a Stouffer 21 step scale.
Exposure FAQ Screen Making Products how to measure exposure

Using the Inverse Square Law of physics, your 40"' would require 4 times the exposure = 48 minutes.

4 Lamps will not increase exposure except where they overlap like headlights. 4 lamps will cover more surface area, at less distance.

When you are bored with guessing, you will buy a 21 step scale & measure exposure.

Search this forum for keyword "halogen" for hundreds of posts.


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## veedub3 (Mar 29, 2007)

40 inches sounds a bit to far away to me. When I had that set up I was between 18 to 21 inches. never more than that though.

Katrina


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## majesticmind (Sep 1, 2007)

With an fx88 emulsion. one 500 watt bulb will be good at 18 iches for 4 minutes. perfect wash out every time.


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## InkedApparel (Mar 18, 2009)

I use a dual cure dxp emulsion and a 500 watt halogen 16 inches of screen and burn for 23 minutes and get a solid 7 everytime ...hope this helps

Inked


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## scrible1980 (Feb 21, 2008)

Thank you for all your help! I managed to get a great looking screen after 35 minutes - I cannot wait until i have my metal halide setup!


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## PositiveDave (Dec 1, 2008)

Just do a screen test, cover your screen with a piece of card and every minute expose another couple of inches, see what happens when you wash out. You're looking for a solid stencil, plus a little bit for comfort.
Be aware that your light will age and you will need to increase your time.
Sort of a home made stepwedge.


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## InkedApparel (Mar 18, 2009)

how would one make there own step wedge...I was thinking about making one in photoshop....kinda like making a rectangle and have 100 black at one end and decrease the screen value by 10 until I have a clear or transparent end..would that work?

Inked


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## PositiveDave (Dec 1, 2008)

It wouldn't be calibrated i.e 50% won't stop 50% of the light, but if you do it by time it works.


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## InkedApparel (Mar 18, 2009)

ahh I see 
how would I calibrate it?

Inked


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## PositiveDave (Dec 1, 2008)

To calibrate a step wedge you'd need a spectrophotometer and too much time on your hands.
Basically you have to measure and control each step so that the light transmission declines at a given rate.
If your maximum exposure is, say, 10 minutes, you want each step reducing the light to 90/80/70% etc.
Plus you need a neutral grey so that you aren't filtering specific wavelengths.


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## RichardGreaves (Nov 7, 2006)

*Making your own step wedge*



InkedApparel said:


> how would one make there own step wedge...I was thinking about making one in photoshop....kinda like making a rectangle and have 100 black at one end and decrease the screen value by 10 until I have a clear or transparent end..would that work?


If you want to do a manual, stepped exposure test, it is easy to make several positive & negative lines 10 inches long.








Cover 9 inches of the positive, and expose an inch at a time for a 'stepped' exposure. 

You will see how longer exposures 'can' choke the lines.









This doesn't really help that much to determine if the stencil is cured/hardened all the way through to the inside of the screen.

When you get bored with turning your vacuum on and off and moving the material that blocks UV energy in your stepped test and making sacrificial tests that can't be used in production, you will buy a US$10 Stouffer 21 Step Gray Scale that can go on* every* exposure you make for the rest of your life.
Exposure FAQ Screen Making Products how to measure exposure

The Stouffer 21 Step Gray Scale is a small film positive with darker and darker filters next to each other in steps. You will get a simulation of 21 different exposures with one exposure. You get visual feedback that shows you how well your stencil is exposed. Start by aiming for a solid step 7.










*Homework*
Exposure FAQ Screen Making Products how to measure exposure


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## InkedApparel (Mar 18, 2009)

I have a 21 step wedge ..I was just wondering if it was possible to do a manual one in photoshop....
Thanks for all the replies

Inked


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## RichardGreaves (Nov 7, 2006)

Any printer you might have, can't make a continuous tone image.

You should make an halftone percentage pattern and use it on every stencil you expose though - to determine how much stencil choking or ink dot gain you have so you to calibrate your art.


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## InkedApparel (Mar 18, 2009)

can you explain that in a bit more detail...I dont really understand ..Im new to exposing screens...
Thanks for any help

Inked


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## mrvixx (Jan 13, 2009)

18 inches for about 5 mins. remove the glass.


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## scrible1980 (Feb 21, 2008)

Thanks again for everybodies input. The Stouffer 21 Step Gray Scale test sounds perfect, my only problem is that i'm in the UK and trying to get one over here is near impossible. Would anyone be kind enough to get one for me and send it across the waters? I can make a transfer via paypal?
Thanks in advance.


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## PositiveDave (Dec 1, 2008)

These guys have them:
Calibration Kit


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## RichardGreaves (Nov 7, 2006)

Stouffer themselves
Ordering

You want to order a T2115.

I see PositiveDave posted a UK source.

I called Stouffer this afternoon and they were no help. Thanks Dave.


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## midwaste (Apr 8, 2008)

It takes me 18 mins at 20" with a 500W(glass removed) to expose to a 7 step with Ulano QX-1 emulsion.
I would guess it will take considerably longer at 40". I have always heard that the distance should be the diagonal dimension of the screen you are exposing, mine is a little closer.

Put a fan running over the glass while you are burning.


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## cmyk (Dec 3, 2007)

i don't understand how this works.

let's se.
i have a good coated screen.
i put that Stouffer 21 Step Gray Scale on the screen (nothing else on the screen) and i expose for a given amount of time, let's say 15 minutes.
i wash the screen and let's say that "right image" (the solid step) is at number 10.
so i need to go back 3 steps, to the ideal number seven.
this means that the 15 minutes must be divided by 3 steps, that is 1.414x1.414x1.414? (according to the mathematic scale in the page richard greaves indicated)
so, 15 divided by 2.827 equals 5.30

???


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## midwaste (Apr 8, 2008)

Typically, the scales have a multiplying factor less than one to account for over-exposure (i.e. time exposed x 0.7 to go back 2 steps, as an example).


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## RichardGreaves (Nov 7, 2006)

*Mystery of a log stepped scale*



cmyk said:


> i have a good coated screen.
> i put that Stouffer 21 Step Gray Scale on the screen (nothing else on the screen) and i expose for a given amount of time, let's say 15 minutes.
> 
> i wash the screen and let's say that "right image" (the solid step) is at number 10.
> ...


Correct. No guessing on the second exposure.

No need to use a whole blank screen. The 21 Step is only .5" x 6". After that, put one on every screen you expose for the rest of your life.

UV energy is lost as it penetrates the stencil - that's why thicker stencils require so much more energy.


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## deadbrokerec (Jul 20, 2009)

majesticmind said:


> With an fx88 emulsion. one 500 watt bulb will be good at 18 iches for 4 minutes. perfect wash out every time.


Your burning from above? And are you using the glass in the halogen light? Please explain.

I have a 500w halogen worklight im using with the fx88 emulsion. What is your setup? Please get back to me asap

thanks


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## majesticmind (Sep 1, 2007)

I took out the filter glass. I am burning from above yes. If you find you are washing out emulsion that is supposed to be exposed just add a minute.


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## RichardGreaves (Nov 7, 2006)

deadbrokerec said:


> Your burning from above? And are you using the glass in the halogen light? Please explain.
> 
> I have a 500w halogen worklight im using with the fx88 emulsion. What is your setup?


There are dozens of posts about exposing with quartz halogen lamps in this forum. Search for "halogen".

Commercial work lights use safety glass to filter UV energy that will damage your eyes when you use it in your basement to fix the water heater.

Screen makers will get the full UV output of the IF they remove the safety glass.

There are many faster, modern emulsions, with much longer shelf lives than Ulano FX88 which is designed for *solvent based poster* or *enamel *inks & abrasion resistance.


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## deadbrokerec (Jul 20, 2009)

RichardGreaves said:


> There are many faster, modern emulsions, with much longer shelf lives than Ulano FX88 which is designed for *solvent based poster* or *enamel *inks & abrasion resistance.


Do you think it's the emulsion? Ive already ruined 6 screens by now. Ive had this emulsion in the refrigerator since 6/17. Ive never had problems like this before, Im really thinking its this emulsion. Ive tried the 500w halogen, no go, and ive tried 4- 4ft. fluoroscent plant light bulbs. and a burn time of 35min and the image is burned and starting to wash off nice, but then other spots on the screen start to wash off as well.

*HELP!!!!!!*


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## RichardGreaves (Nov 7, 2006)

deadbrokerec said:


> Do you think it's the emulsion?
> 
> Ive already ruined 6 screens by now. Ive had this emulsion in the refrigerator since 6/17.
> 
> ...


No, I don't think it is your emulsion. I was explaining the the posts that say "remove the safety glass".

You are ruining screens because you aren't measuring your exposure and you think 35 minutes is enough. UV energy has to move all the way through the stencil and crosslink the sensitizer to make the stencil resist water, so it won't dissolve and rinse down the drain.

*Stencil doesn't stay in the mesh*
If the stencil washes out - it wasn't exposed with enough UV-A energy, so it dissolves with water and rinses down the drain; just like it is supposed to.

*Image area doesn't wash out*
If it doesn't wash out, it was somehow crosslinked with heat or UV-A energy.

You are using a quartz halogen incandescent lamp that is great at VISIBLE light and invisible INFRARED (1,000 degrees F heat), energy. Less than 5% of your output is UV energy you can use to expose your stencils. The grow cycle of plants is usually months, and the sunlight they simulate is weak in UV.

It is very common that you are underexposing because you have a weak UV source or poor positive. There is no problem with what people call *OVERexposure*, instead, calibrate your art to combat *UNDERCUTTING *that chokes fine line openings because of light scatter. Every stencil needs to be completely cured to resist printing.

If your problem was that the image area didn't wash out, this usually means your positive failed to stop UV energy from reaching the stencil.
*
Dime Complete Opacity Test*
To judge if your positive completely stops UV energy, tape a dime or a piece of aluminum foil to the stencil to see if the dark areas of your positive are failing you and letting UV-A energy through to the stencil. If the area covered by the dime doesn't wash out, you have exposed the stencil to UV energy or heat energy and the stencil resists dissolving with water and going down the drain.

To measure exposure I suggest a Stouffer 21 step gray scale to simulate 21 different exposures. 
http://www.ulano.com/FAQ/FAQexposure.htm#Q1

Refrigeration at 42 degrees F does little to prevent the decay of diazo sensitivity from being saturated with *water*. It does not spoil like food. 42 degrees is 10 degrees from ice cream so let your emulsion return to room temperature before coating or you will get drips. 

For the same money you can get a modern SBQ sensitized emulsion that is much faster and has a shelf life of 18 months.

Good Luck


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## RideOutWear (Feb 27, 2010)

PLEASE HELP!!! i am using the same set up my light is 18" above my screen and i am using ulano rlx pink emulsion. i have been at it all day and cant get the image to wash out. i tried 12.5 min first no luck, then went to 25 still nothing, then to 40 still nothing. right now i am out of screens with emulsion on them so i have to wait until tomorrow to go at it again. you think the time could be less than 13.5. i thought maybe i over exposed them.


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## selanac (Jan 8, 2007)

What are you using to wash them out, pressure washer, hose, or water massager?


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## RideOutWear (Feb 27, 2010)

first i used a hose with a high pressure nozle, then i used a gas powered pressure washer.


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## InkedApparel (Mar 18, 2009)

if you can not wash the image area out..then it is over exposed......12.5 minutes must be to long...cut the exposure time in half and see if the image washes out ...if not then cut that time in half...I have never used the type of emulsion you are using so I can not give you a time to start with.....do yourself a favor and get a 21 step wedge exposure calculator...use it on every screen you expose ...this is the best way to determain exposure time. good luck

Inked


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## RideOutWear (Feb 27, 2010)

how will i know if it is under exposed?


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## BroJames (Jul 8, 2008)

RideOutWear said:


> how will i know if it is under exposed?


Areas that are not supposed to be washed out got washed out should be a good indication of underexposure. Lighter emulsion shade should also be a good indication.

This is kind of an old post but I see that the exposure time varies significantly. It may be due to the emulsion but maybe some other factors too.

I have been trying to find the stouffer here (Philippines) and has been unsuccessful so far. I am now using mercury lamp but used to use a 500w halogen. At 20-24"(sometimes farther) I got good exposures at around 5(4:45-5:30) minutes with most emulsion including often used Murakami's TXR. For washout, I use a garden hose with nozzle and would estimate the pressure exerted at medium.

My exposure time is more in line with Darin, Dan and Mrvixx. If Midwaste and Inked got solid 7 for their longer exposure times(even allowing for normal variances across emulsion) then maybe I have been underexposing. Emulsion holds though with stronger than "medium" nozzle pressure.

Lately, I am not using the nozzle though and washes the emulsion with slight hose pressure.

I've just visited their website and can;t seem to find the T2215.


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## RideOutWear (Feb 27, 2010)

ok i just tried 5 minutes and nothing would wash out. and when i took the screen off the light i couldnt see my design in the screen at all usually u can


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## BroJames (Jul 8, 2008)

RideOutWear said:


> ok i just tried 5 minutes and nothing would wash out. and when i took the screen off the light i couldnt see my design in the screen at all usually u can


What distance is the lamp?

From what you posted, seems like a case of overexposure. But if you are using a 500w halogen and the distance is anywhere more than 12" I would say that the problem is more likely to lie in the emulsion or improper film positive to mesh contact. 

But then, if the emuslion has expired or is improperly mixed more often the case would be a washout. And I have not heard of quick burning emulsions that is overexposed by a 500w halogen in 5 minutes.

Are you using a vacuum hold down or is the film positive pressed firmly against the mesh and glass?


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## InkedApparel (Mar 18, 2009)

what type of emulsion are you using? is it a dual cure or a direct emulsion?
if a dual cure , did you mix the diazo sensitizer in? and how old is the emulsion?
how dark are your films? there are many things that could be the problem here......

Inked


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## RideOutWear (Feb 27, 2010)

emulsion was just bought 3 days ago it is a dual cure. but i did get it i was over exposing, im kind of a newbie when it comes to burning i use to have someone do it for me until i got my own exposure unit. it is washing out good now, but one thing i still notice is the emulsion is getting kind of gooey to the touch after i wash it out and sit it up to dry. i let the emulsion dry for 24 hrs before starting.


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## InkedApparel (Mar 18, 2009)

dual cure diazo will be slimmy to the touch on the squeegee side if the light source is above the screen...this is normal....take a piece of newspaper and lay it inside the screen and pat it dry ...this will soak up the excess water from washing out the stencil...let dry near a fan or put it outside to airdry...becareful , sopmetimes the diazo likes to run into the image area when drying.....make sure you get all the excess water off the screen to avoid this.

btw - what was your final exposure time?

Inked


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## RideOutWear (Feb 27, 2010)

ok thanks very much for all the help!!! my final time was 4:30m i had some pin holes wash out in my last screen so i may attempt 4:45 and see if it turns out perfect. lol


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## InkedApparel (Mar 18, 2009)

pinholes arent from time..they are from dust or a dirty film.......clean the glass and film before exposure...make sure there are no dust particles on either.

Inked


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## RideOutWear (Feb 27, 2010)

Ok thank you. I didn't know that I learn something new every day


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## RichardGreaves (Nov 7, 2006)

*Ulano dual-cure RLX image doesn't dissolve*



RideOutWear said:


> i am using the same set up my light is 18" above my screen and i am using ulano rlx pink emulsion.
> 
> *i have been at it all day . *
> 
> ...


Exposure is easy.

The purpose of UV exposure is to change the stencil from something that will dissolve with water, into something that _*won't dissolve*_ with water or breakdown during a print job.

Since you can't get the image to wash out, the stencil has done it's job. 

If the image area doesn't *dissolve*, above all else, it usually means your positive failed to stop UV energy from reaching the image area. UV-A energy leaked through the positive like a bad raincoat and only cross linked a crust on the bottom surface of the image area so it wouldn't dissolve with water and rinse down the drain.

*Dissolve Time*
To establish a base time for washout, make a very small coating (3 inch by 6 inch?), on a screen and let it dry to the touch - then take it to your washout area and time how long it takes to dissolve.

Don't expose it, just wash it out. That is your standard time for washout for that mesh & coating.

If you're developing outside, in the UV rich sunshine, that's one of your problems.








_Teaching screen making 1988 Hawaii Jim McCortie xVP Autotype_

*Positive comparison*
Next time you expose any screen, test if your positive completely stops UV energy. Tape a dime (or any thin coin), or a piece of aluminum foil to the to the outside edge of your stencil. No light will penetrate the dime and that area should wash out like a dream compared to your positive.

*Buy a Stouffer T-2115*
To measure stencil hardness (resistance to developing or cleanup solvents), I suggest a US$10 Stouffer 21 step gray scale to simulate 21 different exposures. This is a standard photographic darkroom test positive that's been used since the 1930's.

Exposure FAQ Screen Making Products how to measure exposure (http://www.ulano.com/FAQ/FAQexposure.htm#Q1)


*Homework*
http://www.t-shirtforums.com/screen-printing/t109276.html#post638392

http://www.t-shirtforums.com/screen-printing/t108761.html#post635432


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## RichardGreaves (Nov 7, 2006)

*Can't find Stouffer T2115*



BroJames said:


> I've just visited their website and can;t seem to find the T2215.


Stouffer web site T2115 section
Transmission Step Wedges

Any serious photography shop that sells dark room supplies should have a transmission gray scale foe photographic enlarging or printing.

List of known USA distributors on the Internet 
http://www.ulano.com/support/training.htm#21


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## RichardGreaves (Nov 7, 2006)

*Pinholes*



InkedApparel said:


> pinholes arent from time..they are from dust or a dirty film.......clean the glass and film before exposure...make sure there are no dust particles on either.


Coating too quickly causes foaming in the emulsion coating tray, and can cause air bubbles in the mesh openings that break. 

Not filling the mesh holes completely results in a thin, weak stencil that breaks.

High humidity and insufficient drying.

Emulsion on the squeegee side of the mesh is more difficult to cure/harden properly during exposure. The inside of a screen suffers from abrasion by the squeegee during printing, causing pinholes and breakdown.


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## InkedApparel (Mar 18, 2009)

see ..now I learned something new today


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## RideOutWear (Feb 27, 2010)

thank you Richard very good post! i did finally get to the print stage with this design with all the info i got from here!!


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## BroJames (Jul 8, 2008)

Nice to know you got it at 4:30m. Would you happen to know what went wrong earlier?


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## RichardGreaves (Nov 7, 2006)

*Printwear Seminars in Tampa*

RideOutWear

Keep your eye on nbmshows.com for new Printwear Show 'seminars only' show in Tampa September 2010.


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## RideOutWear (Feb 27, 2010)

BroJames said:


> Nice to know you got it at 4:30m. Would you happen to know what went wrong earlier?


i over exposed it by a lot. i read on here on a bunch of the 500 watt exposure unit threads that 12.5 is the time even you tube videos said that so i went with it, then being inexperienced not knowing signs of over exposure, i kept going up in time when i couldnt get it to wash out, now that i know how all this emulsion vs uv works i know what to do when i get a bad wash out or a no wash out!!


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## RideOutWear (Feb 27, 2010)

*Re: Printwear Seminars in Tampa*



RichardGreaves said:


> RideOutWear
> 
> Keep your eye on nbmshows.com for new Printwear Show 'seminars only' show in Tampa September 2010.


ok will do thank you for all the advice!


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## InkedApparel (Mar 18, 2009)

also ...different types of emulsion have different burn times......be sure to check which type of emulsion you are using...

Inked


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## nativesonjls (Jun 6, 2010)

Lets not forget the stencil and or stencil material, I use vellum paper doubled so I had to add between 20 and 25 percent for each layer, clear transparency negate that and if its not completely opaque it can go the other way........man this can get frustrating at first.....my time with the 500 watt at 20 inches was 19min30sec but adding another 500 cut it to 9min30sec. A metal halide 1000 watt should drop me to 3 to 4 min plus or minus, they output more uv from what I've reviewed


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## RideOutWear (Feb 27, 2010)

what brand 500 watt light are you using? i have 1 and my time was 4:30


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## OTFINC (Mar 24, 2009)

ok It shouldnt be taking longer than about 12 minutes. make sure your light has the glass removed. otherwise that glass is uv resistant. does your light look similar to this set up?? Screen Exposure Stand


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## RichardGreaves (Nov 7, 2006)

*Not Over Exposure- Poor Positive*



RideOutWear said:


> i over exposed it by a lot. i read on here on a bunch of the 500 watt exposure unit threads that 12.5 is the time even you tube videos said that so i went with it,
> 
> then being inexperienced not knowing signs of over exposure, i kept going up in time when i couldnt get it to wash out, now that i know how all this emulsion vs uv works i know what to do when i get a bad wash out or a no wash out!!


As an example - If you use a dime to stop UV energy (even with a 2 hour exposure), it will wash out like dream.

Since you're using a diazo dual-cure, I don't think you actually cured your stencil. You just succeeded in getting the image to dissolve, which doesn't mean you completely hardened the stencil.

Under exposed stencils are hard to reclaim. Completely cross-linked sensitizer is easy to reclaim.

*Homework*
It's time to go back and re-read Post#29 (just before your original post) & Question why you chose to use Ulano RLX instead of a faster dual-cure or SBQ sensitized emulsion for your learning stages.

Please do me a favor ask the person that suggested or sold you emulsion, how you should measure exposure hardness - especially to a beginner.


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## InkedApparel (Mar 18, 2009)

@ Greaves - 

what type of emulsion would you recommend for the complete beginner? I know when I first began I went with a dual cure right out of the gate..only because this is what almost everyone was using in every video I watched on youtube.com

now would you say a dual cure is better for a begginer or maybe a direct emulsion due to its longer shelf life or something completely different ?

Inked


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## nativesonjls (Jun 6, 2010)

I used EX1 from screen printing supplies, its a dual cure so remember to cure the second time after you washout and dry, 
1) very simple to use 
2) good for both waterbased inks and plastisol 
c) slow cure time compared to some other types but you have time to work with it, (use yellow bug light) 
d) cures with low yield uv sources like halogen lights (min 500 watt) *halide is better* 
e) you can buy a brush on coating for a third or triple cure to prolong the life of the screen, you still have to mix the two parts just like diazo emulsions
ScreenPrintingSupplies.com - Screen Printing Supplies, Equipment and Ink at discount prices!
I only bought a qt because I only have eight screens the ones with the longer shelf life also cure very quick which means less time to work with the emulsion once to setup to cure can't make as many adjustments but if your set up is right you should not need this time.


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## RichardGreaves (Nov 7, 2006)

*What stencil for a beginner?*



InkedApparel said:


> @ Greaves -
> 
> what type of emulsion would you recommend for the?
> 
> ...


The best stencil for a complete beginner is *direct film*. Film that is applied directly to wet mesh and adheres with capillary action. Like sticking a postage stamp to wet mesh, the water softens the un-hardened/un-cured film and now the film is sticky. About 50% of the film embeds in the mesh, but the stencil surface is as smooth as the polyester it's coated on at the factory. 

Want high solids; film is 96% solids.

6 year old Jennifer can make a perfect stencil in one hour total, on her third try, that's better than what a 30 year veteran like me can do in 3 days with direct emulsion *of any kind.*

The drying time for direct emulsion is it's biggest drawback. When the water evaporates, the stencil shrinks around the mesh fibers and takes on the texture of the mesh. This rough stencil surface (high Rz) is no real problem for textile screens, but a disaster for smooth surface (low Rz) and non-absorbent substrate printers

Choose your stencil to resist your ink & cleanup solvents, then consider if you need fine line reproduction.

Water or solvent-based ink needs water or solvent resistance. The best use diazo sensitizer which requires more UV energy to cross-link than SBQ or acrylate sensitizer.

Water or solvent in the ink attacks the raw, inside of underexposed screens and can lead to breakdown on the press.

Plastisol is like salad dressing. ANY EMULSION will work fine, even under exposed emulsion.

For the best fine lines use a dual-cure (dual sensitizer), which usually means adding diazo sensitizer your self. 

Diazo is stable after mixing it with water for 4-6 weeks, then it becomes un-stable and exposure times change. SBQ and acrylate sensitizer added at the factory and aren't effected by water so they are stable for 18 months from manufacture. If you are measuring exposure, you can judge how long to expose as it gets older.

Pot life is not an absolute - merely a manufacturer's suggestion, because they don't control the environment after the product leaves the factory. Milk on a picnic table in summer will not last until the use date printed on the carton.

Diazo has an advantage over sensitizer because it changes color when it's exposed with UV energy - SBQ and acrylate don't. This is why a free, traditional, manual, stepped exposure test is not very good at helping novice screen makers determine exposure. Read post #29 in this thread.

Negligent screen printing distributors that are "supposed to know better", should do a better job of helping novice screen makers understand how to measure exposure. I can walk up to a rental counter in any airport and rent a car in 5 minutes because I have to show a license. 

Stencils aren't dangerous like cars and most grocers don't check if you're qualified to expose steaks to Infra-Red energy in the back yard, but a novice screen maker hasn't spent any experience determining how to measure stencil cure. We can't cut it open and look or taste it like you can a steak.

When I become King - all screen makers will be forced to buy a US$10 Stouffer T2115 Transmission Gray Scale to measure exposure, because under exposure is the #1 cause of screen problems.


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## nativesonjls (Jun 6, 2010)

*Re: What stencil for a beginner?*

Amen.............if the sales man only told someone


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## RichardGreaves (Nov 7, 2006)

*Dual-cure process?*



nativesonjls said:


> I used EX1 from screen printing supplies, its a dual cure so remember to cure the second time after you washout and dry, ...


Did someone *actually *tell you that dual-cure means expose before and then after exposing?

Dual-cure means two different sensitizers - SBQ or acrylate sensitizer with diazo added by the screen maker.


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## nativesonjls (Jun 6, 2010)

*Re: Dual-cure process?*

I made that mistake, I'm still new at this, they were talking about post curing with the dual cure and I made that jump, thanks for setting me straight on that, every little bit helps. Forgive my ignorance on this process, pushing the edge on research on the process, lot to learn and little time. If I make a mistake on a post correct me, I'm thick skinned, I need to know all I can.

You know your trade, already read several posts by you, so I will follow more of your posts and try to get up to speed I worked in the graphics end for years in school on the paper, 4 color 12 page tabloid size paper, and was the senior graphics editor my last year, sent tons of printed and pasted final layouts to the print shop, lots of trapping and chocking, tile matching and past-up, etc. and then in the Eng. and Architectural end for years, started in the print room but that was blue printing then digital output from autocad, then in the office as a cad tech after the drafting tables were retired, but no shop time myself, so I'm pushing the learning curve, layed off ya know and trying to setup a small at home printing operation to try and supplement my income.


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## selanac (Jan 8, 2007)

This could open up a whole new Can or Worms about what salespersons say and don't say, lol.


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## nativesonjls (Jun 6, 2010)

Well if I just knew what I know now just 2 weeks later I would own a single station 4 color press (currently single station single color), flash unit 18x18 (currently 16x16), heat press, plus the materials I really need for what I want to do like some 180 to 230 screens instead of all 110, and would not have put myself through so many changes to learn some of this if I had been on this site before I started purchasing what I did, for about the same money................but salesman gotta eat to I guess.


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## RideOutWear (Feb 27, 2010)

i have another question, when my emulsion is dry dots show up on the scren they look like the emulsion was dripping but its not. just wondering what causes this, it seems like the screens higher on my rack have more of them.


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## BroJames (Jul 8, 2008)

RideOutWear said:


> i have another question, when my emulsion is dry dots show up on the scren they look like the emulsion was dripping but its not. just wondering what causes this, it seems like the screens higher on my rack have more of them.


I have always wondered what really cause them. I was thinking maybe that the air/wind from the blower may be too strong or that my rack was not level enough. 

Did you mix your emulsion and let it settle half an hour or more before coating? That, among other changes seem to solve that problem for me.


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## nativesonjls (Jun 6, 2010)

I had these on my first screens but someone suggested flipping the screen and pulling again with the thin edge on both sides to remove any uneven emulsion ( just removeing, not applying) from the first screen application, then dry and apply more coats as needed for the stencil thickness, haven't had any on my last 8 applications, I have been applying 1 and 1 with a dry then a second coat on the stencil side and a dry they have been smooth as silk............. so far

The video on catspit productions said it takes a while to learn to apply even pressure during application and the coat is sometimes nonuniform, my experience is it will run, pool (the dots), or drip, I almost positive it was the emulsion video he did, or the scoop coater.


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## RideOutWear (Feb 27, 2010)

i let it sit for an hour. but i did cure the problem i simply put a small fan on low next to them and screens look perfect today.


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## selanac (Jan 8, 2007)

We had that problem before too. I thought it was due to too much emulsion so we applied less. If I remember correctly, we switched to a Scoop Coater.


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## BroJames (Jul 8, 2008)

RideOutWear said:


> i let it sit for an hour. but i did cure the problem i simply put a small fan on low next to them and screens look perfect today.


If that is your case then poor ventilation or air circulation was your main problem.


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## nativesonjls (Jun 6, 2010)

Along the same lines, I use a lot of tape and block out, why couldn't you just pull your first emulsion coat from frame edge to frame edge then pull the center front and back, cure as normal and have real stencil on most of the screen, when ever I do a color change and clean the ink I lose some of the block out, have to tape anyway. If I reclaim the screen tape residue is a monster even with goo be gone. 

Then you just tape the front, and clean up doesn't wash the block out away, and you save tape, use block out on pinholes if needed (like close to graphic), I use tape on any pin holes I can because I have to reapply the block out if its washed away. Just curious, I know you use more emulsion but the cost can't be much more than all the other materials and time with them.


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