# Exposure times for different mesh counts?



## Chrisxcolour (May 11, 2014)

Hey guys!

I've recently invested in some new screens and being the prat I am I assumed stuff would remain the same. How naive, huh?

I've gone from using white mesh 43t and 62t screens and burning them for 4:30-4:50 - depending on the detail of it - to yellow mesh 90t and 120t 

I've been having difficulty getting the emulsion out of the screen (Admittedly it's happened a lot recently, even with the lower mesh counts). I've often resorted softly cleaning it out with a scourer pad. I'm not sure what I'm doing wrong! 

I use a pretty powerful shower head to get it all out. Wetting, soaking for 30 seconds, wetting and soaking again. Then washing out. 

Any help on this would be appreciated!

Thank you


----------



## spotcolorsupply1 (Jan 17, 2013)

Yellow mesh will burn at different times than white mesh. You might want to lower your burn time down.


----------



## matt gilliland (Jul 24, 2014)

Hello,

What emulsion are you using and how old is it?

What type of film positives are you using?

What type of light source?

My best advice to anyone would be to use an exposure calculator to determine proper exposure times. Then, every so often or whenever you change something use it again.

Matt


----------



## maddogprints (Nov 19, 2012)

Higher mesh , usually has a lower burn time , so many variables such as what exposure unit you have the strength of light in unit , best thing is to get a exposure calculator


----------



## Chrisxcolour (May 11, 2014)

Thanks for the replies guys! I actually lowered the burning time by 20 seconds anyway.

Using Amex Dual Emulsion. MIxed about 7-8 weeks ago so it should be good for another 4. 

I'm just using clear R LAZER film for my positives with Black Max ink

I'm using an open face silver exposure unit. 8 bulb model from Dave Roper


----------



## jeron (Jul 16, 2012)

I believe the biggest reason is higher mesh usually has a thinner stencil... unless you coat more... so less emulsion = less time

Thanks,
Jeron


----------



## Chrisxcolour (May 11, 2014)

Yeah I normally only do a 1/1 coat. I feel like me not having a pressure washer to get it out is hindering a lot as well.

I'm worried that it'll just tear the screen if I use one of them.

I've already tore a 120t screen while washing emulsion off it with a dish cloth and minimum pressure (Which still baffles me) so I don't wanna make a habit out of it haha


----------



## jeron (Jul 16, 2012)

You shouldn't need to use a pressure washer to expose your screen... just normal tap water through a garden hose sprayer.. I use the one with different settings and have it set to the shower mode... I wet it down on both sides, let it sit for about 30 seconds then wet it down on both sides again and wait another 30 seconds... do this until you start seeing the emulsion start washing out, then you can just spray out from one side till all the emulsion is gone... then a quick wash of both sides to make sure there is no residue left over..

As a test take a screen that you just coated that is ready to burn, but before you burn an image, put that in your washout area and wash it out using just garden hose pressure... it should wash out very easily. If it doesn't you have problems with your emulsion or something... you can use this as basically a base this is how easily your screen should wash out after exposure as well... if not your burning for too long most likely..

Thanks,
Jeron


----------



## matt gilliland (Jul 24, 2014)

I agree with what was said about washing out the un-exposed screen, it's a good idea. With all things being right, finer mesh should develop more easily than coarse mesh. 

Please don't take this the wrong way but Laser film positives are probably some of the least dense available so, you may be over exposing.

I can't stress enough how important an exposure calculator is to your operation. They're about 10.00 and worth their weight in gold. Start with a new can of emulsion and spend a few hours "profiling" your exposures. It will make your life easier.

Anyway, my .02.

Matt


----------



## Chrisxcolour (May 11, 2014)

Thanks! I'll be sure to try that. Hopefully I'll get some answers soon, eh!

Unfortunately these are the only film positives I can get in from out supplier! These are them on the site

Okay I'll look into an exposure calculator. I'm still busting a very home set-up right now and finding my bearings with all of this. A lot to take in at once haha

Thank you for the responses though, guys! You're all top geezers


----------



## killroy (Feb 16, 2014)

I would definitely get an exposure calculator. In the beginning my films weren't that dark so I had to really dial in my exposure times. When you can afford it or want to invest more money get a good film output setup. Having really dark films takes all the guess work out of it.


----------



## sben763 (May 17, 2009)

Just do a step wedge test. Save your money and don't buy a calculator. Here is why. A calculator will get you your exposure times for the calculator. The are made on very clear image setter film and the coated with the steps. Most inkjet films are slightly milky and if your films aren't as dark at the calculator then the calculator time may not work and depending on the clearness difference makes it even tougher. A step wedge test uses you films to calculate your times. 

Depending on the emulsion you are using can make a difference as well as you exposure unit. Back when I used a black light unit I would have to expose different times for spot colors vs halftones and different mesh. I still adjust 15 sec between a 272 mesh vs a 128 mesh but with a single point I don't adjust any times for halftones vs the spot colors. The only reason for adjusting times between mesh are that finer mesh doesn't get as much EOM ( emulsion over mesh). There is also a fiber optic effect and the more threads the more the effect. This is why mesh is dyed yellow to combat the fiber optic effect. 

If you coat a screen with a 1/1 and a screen with a 2/1. You will need to increase the exposure time on the 2/1


----------



## jeron (Jul 16, 2012)

I agree with using a step test... although I have never used it, I recall seeing a calculator that you place over your film that has different densities of black... then you just burn for a set time and washout then adjust your time based off of the different multipliers... but it is still using your film add the base... it basically takes away the need to shut off your unit to move the wedge manually.. if that makes sense..

Thanks,
Jeron


----------



## jeron (Jul 16, 2012)

Here it is... it's by ulano.. you can use their calculator as the base or put the wedge part over your own films..



Thanks,
Jeron


----------



## Chrisxcolour (May 11, 2014)

Awesome I'll definitely do that. I've found a free download of one so I'll put it to the test later and see what happens huh!
You guys are great.

SUB QUESTION:

What does everyone use to clean off inks and emulsion etc? I use either scourer pads or dish cloths. I've been advised not to use scourers so much as it can damage the fibres (Causing the tears I had the other day. Oops) but what do you guys suggest?


----------



## jeron (Jul 16, 2012)

I use the scrub pads.. like the one in the pic.. except the pads are white... I scrub pretty hard sometimes and never had a screen pop... you shouldn't have a problem using these, it's something else hurting your screens

Thanks,
Jeron


----------



## killroy (Feb 16, 2014)

If you use the right stuff you shouldn't have to scrub. I use concentrated emulsion remover follow up the "The Pink Stuff". I use a sponge that you would use for a car and just apply to both sides and let it sit for 1 min or so and wash out. I never like scrubbing my mesh!! I also spray my screens down with 50/50 water vinegar solution and let dry. The vinegar will neutralize any acids that may be left over. I also use some clean up cards to get most the ink off. Less ink = less hassle. Make sure you don't let your screens sit long before you clean them. The longer they sit the harder they are to clean. I usually try to clean mine every 2-3 weeks. If left any longer It will have an tendency to ghost more.


----------



## Chrisxcolour (May 11, 2014)

Yeah I've taken to using cloths instead of scouring pads. Especially for the emulsion removing. 

I get ghosts on nearly everything I do and it's kind of annoying haha my haze remover doesn't seem to do a great deal. I've put one screen through the process twice and it hasn't changed a lot at all. It still prints through but the mesh looks messy and I don't like it


----------



## sben763 (May 17, 2009)

Chrisxcolour said:


> Yeah I've taken to using cloths instead of scouring pads. Especially for the emulsion removing.
> 
> I get ghosts on nearly everything I do and it's kind of annoying haha my haze remover doesn't seem to do a great deal. I've put one screen through the process twice and it hasn't changed a lot at all. It still prints through but the mesh looks messy and I don't like it


Use non scoring pads like shown a few post back. Is the ghost image you seeing clear? If so it will never go away. A ghost image to be concerned with will have the ink color to it. Just ink stains is the only thing to be concerned with. 

The clear ghost images are from the squeegee flattening the fibers. It can also be a UV bleaching of the mesh. Neither of these conditions will affect exposure.

For emulsion remover Beanedoo. For a dehazer enviro haze from CCI doesn't affect the mesh but with any dehazer keep off the glue areas.


----------



## Chrisxcolour (May 11, 2014)

RIGHT GUYS.

Exposure calculator has been used on an available white mesh 60t screen. It was interesting and I'm really baffled by the results haha. I did 45 second intervals between moving to each square. I expecting number 1 or 2 to be the best exposed (I normally expose screens for 4 minutes and 30-50 seconds) and the first 2 to just wash out completely without showing the design. 

The only one that washed out was the last set of squares and writing - which had only been exposed for 45 seconds. The others barely came out - even after rubbing them down. All the details and sharp lines had been kept. Even the 0.5pt text and lines! 

So now I'm baffled. I've been told to had exposure times at 3-5 minutes for the duration of my getting into screen printing. Can someone give me answers to this haha

Thanks a bunch!


----------



## sben763 (May 17, 2009)

Did you change emulsions? What type of emulsion dual cure(you have to mix the diazo) or photopolymer (premixed). It could be very possible especially with the photopolymer that previously the humidity was very high. Most Photopolymer emulsions will reabsorb humidity even when totally dried. If the emulsion is above 45% or above it will take much longer to expose and you run a high risk of blow out. The last few days here in my religion have been much drier then the past 8 weeks. I run a dehumidifier anytime I have screens coated even when storing as I keep 24 screens ready at all times. 

So it very possible the humidity is low now and your screens where dry. If you use dual cure it is important to dry in low humidity but can be stored in higher humidity after dry.


----------



## Chrisxcolour (May 11, 2014)

sben763 said:


> Did you change emulsions? What type of emulsion dual cure(you have to mix the diazo) or photopolymer (premixed). It could be very possible especially with the photopolymer that previously the humidity was very high. Most Photopolymer emulsions will reabsorb humidity even when totally dried. If the emulsion is above 45% or above it will take much longer to expose and you run a high risk of blow out. The last few days here in my religion have been much drier then the past 8 weeks. I run a dehumidifier anytime I have screens coated even when storing as I keep 24 screens ready at all times.
> 
> So it very possible the humidity is low now and your screens where dry. If you use dual cure it is important to dry in low humidity but can be stored in higher humidity after dry.


No, nothing has changed at all. The temperature in the UK over the last few days, if anything, has dropped and has been raining a lot as well. 

This is the emulsion I use Though, I'm keen to try out another brand and is premixed to see how it works for us. 

I'm just really stumped as the only part of the stencil that washed out properly and kept detail (Even really fine detail) had only been exposed for 45 seconds. The next part had been exposed for 1 minute 30 seconds and it came out good - after rubbing it down (I don't have a pressure washer. Only a shower head. It's pretty strong!) So I'm dead confused haha


----------



## Chrisxcolour (May 11, 2014)

Okay! I tried to put this image up the other day and it wouldn't work. 

As you can see boxes 1-6 are having none of it. 7 has come out okay but still needed some persuasion and 8 came out SUPER clean (When I rubbed it down a little it started to come off. But initial soak and washout was real nice) 

Box 8 had only been exposed for 45 seconds. So I'm really confused - why have I been told to expose for 4 minutes plus? Why has my life become a sham in less than 6 minutes? 

Opinions on this please!
Thank you


----------



## jeron (Jul 16, 2012)

What kind of exposure unit do you have? Metal halide? Fluorescent tubes? Halogen?

Different lights expose at different rates.. for example, I started out with a 1000 watt halogen and my burn time was about 7 minutes... upgraded to a 5000 watt metal halide and my burn time with the same emulsion and screens went down to 17 seconds.. 

Thanks,
Jeron


----------



## Chrisxcolour (May 11, 2014)

jeron said:


> What kind of exposure unit do you have? Metal halide? Fluorescent tubes? Halogen?
> 
> Different lights expose at different rates.. for example, I started out with a 1000 watt halogen and my burn time was about 7 minutes... upgraded to a 5000 watt metal halide and my burn time with the same emulsion and screens went down to 17 seconds..
> 
> ...


This is the exposure unit I use

So it's not even anything super. It's entry level, cheapest that we could get to start out. Which is why I'm even more confused haha


----------



## Chrisxcolour (May 11, 2014)

Anyone else got opinions on this? 
Thanks


----------



## jeron (Jul 16, 2012)

Did you try and wash a fresh screen out that has NOT been burned yet? If not you should... this is the easiest way to know how easy or hard your emulsion should wash out after you expose an image. You may be thinking it should be easier or harder than it should and that will let you know


----------



## Chrisxcolour (May 11, 2014)

jeron said:


> Did you try and wash a fresh screen out that has NOT been burned yet? If not you should... this is the easiest way to know how easy or hard your emulsion should wash out after you expose an image. You may be thinking it should be easier or harder than it should and that will let you know


We don't have any screens here that are completely fresh. I'm thinking if I can do a short exposure, wash out then expose again. That would be good!


----------



## maddogprints (Nov 19, 2012)

we use scouring pads , red ones and we have screens that last for long periods of time


----------



## jeron (Jul 16, 2012)

Sure that would work but it's just an extra step that's not needed... need time you get a fresh screen try out out... it may take you a little time and work to figure it out but it will be worth it

Thanks,
Jeron


----------

