# Someone please help! difference is between yellow mesh and white?



## aust1025 (Mar 1, 2007)

Can anyone tell me what the difference is between yellow mesh and white?

I am having a heck of a time with my burn times and the chart that came with my
emulsion is for yellow mesh with a 305 count and i am using white with a 155 count. I built my exposure unit out of a glass window and a tube fluorescent shop light. It works really well on large images but smaller images with finer detail i just cant get it right. Any help would be greatly appreciated as i have been working 14 hours a day washing out and reburning screens over and over and over etc...


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## aust1025 (Mar 1, 2007)

Il rephrase and get to the point, lol.

I guess my real question is, the chart for burn times that came with my autosol 2000 emulsion says that a burn time of 6 - 7 minutes is fine for a fluorescent light such as mine, the problem is the times stated are for yellow mesh and i am using white. Is the? burn time still accurate


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## Don276 (Feb 26, 2007)

I believe there shouldl'd be a difference with burn times. I have both white and yellow mesh and have not had any problems. Some manufactures of the mesh use the colors to color code the mesh counts. 110-white 220 yellow etc. The finer the detail though the higher the mesh count you would want to use..( i have had that problem in the past also.) Hope that was some help.


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## Fluid (Jun 20, 2005)

The dif between yellow and white mesh is that yellow mesh will not refelct the light like the white mesh does. Yellow mesh will generally burn quicer than white.

What is your current burn time?

What exactly is happening? Not totally washing out. Some but not all areas?
need a lil more info


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## aust1025 (Mar 1, 2007)

my latest burn time was 25 minutes and the image almost came out but some of it washed away, i believe that is from over-exposure right?


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## aust1025 (Mar 1, 2007)

my screen is a white mesh at 155 count.


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## Fluid (Jun 20, 2005)

If the image(emulsion) washed off the screen that it was either undercured or your sdcreen wasnt reclaimed (degreased) properly. Most likely it wasnt cured/exposed long enough.
25 min is extreme. You might want to add a couple more bulbs.
Emulsion is cured from UV light, flourescents will do the job yet take forever. Adding some more might help.


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## aust1025 (Mar 1, 2007)

Here is a photo i shot, the arrows show where it isnt washing out and in the middle. the line is suppose to go all the way across and it blew right out when 
hit it with the water.


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## aust1025 (Mar 1, 2007)

Unfortunatley i am stuck with what i have for this job, i will add a better light source after this ordeal. Ughh what a nightmare, this job was due about 2 days ago, lol.


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## Fluid (Jun 20, 2005)

I feel your pain.
You having two issues that seem to have dif possibilities that may be affecting the screen.

The image washing of is more than likely due to the emulsion not adhearing to the screen properly when it dried. Possible cause poor reclaim like I mentioned before.

The image not washing out looks like you actually over exposed the screen.

I would contact your screen print supply company and get yourself an exposure calculator. youll need to run some test exposures yet this will help you to find the correct exposure times with your equipment.

Whish I could help more. If you know a local screen prit shop maybe they will burn the job for you. Put a dry coated screen in a black garbage back and have them burn. Just to get the job printed.

Good Luck


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## aust1025 (Mar 1, 2007)

I was using Mr. Clean to degrease the screen.

I also am using speedball screen wash to reclaim, any other hints that could help?


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## Fluid (Jun 20, 2005)

stay away from mr clean. get an industry degreaser. If you cannot get a dishsoap with no perfumes/scents. The oils will cause the emulasion to not adhere properly.

Mr clean might be too harsh.


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## aust1025 (Mar 1, 2007)

I am running some tests right now, my flourescent tube lights are weak at best, lol. I do have some of the spiral type flourescents for a regular outlet and those work alot better. 

My plan is to go and get some better tube type flourescent's with a better uv rating and that should be the fix to a 60 hour nightmare, lol.

Thank you for all your help.

-Dave


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## Oritron (Feb 26, 2007)

aust1025 said:


> I am running some tests right now, my flourescent tube lights are weak at best, lol. I do have some of the spiral type flourescents for a regular outlet and those work alot better.


Hey Dave,

This may constitute as a bit late (I was just searching the forum to find out why someone would want a yellow screen, which I learned the reason to in this thread), but maybe I can share my experience.

First, those spiral bulbs are called "Compact Fluorescent," and from my past experience with photoresist on circuit boards, I can say that those are worth staying away from. You don't get an even enough light distribution.

Second, I make screens with plain fluorescent tubes, and it used to go really slow - I'd give it an hour and a half minimum. That was about a foot away from the bulbs.

Since then, I found that a foot away is too far. I now hold my screen closer to the bulbs (maybe in the order of two inches away? The fixture is too big for me to get closer), and the screen is done in around four minutes. I think one day I will build a proper exposure unit, so that it's less of a guessing game, but you get used to the look of emulsion when it's done.


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## RichardGreaves (Nov 7, 2006)

*Re: Difference between yellow and white mesh?*



aust1025 said:


> Can anyone tell me what the difference is between yellow mesh and white?
> 
> I am having a heck of a time with my burn times and the chart that came with my emulsion is for yellow mesh with a 305 count and i am using white with a 155 count. I built my exposure unit out of a glass window and a tube fluorescent shop light. It works really well on large images but smaller images with finer detail i just cant get it right.


Glass always prevents some of the UV light from exposing your stencil. The thicker the glass the greater the filtration. Was your salvaged glass from a store window that had a UV filtration coating to prevent displays from fading?

Lamp distance is CRITICAL. Pack them tight and 4" to 6" from the glass. At best fluorescent lamps only use 40 watts of electricity, and that isn't the output, but the input wattage. The Autotype exposure times are for commercial exposure units and may not relate to your home made setup.

How many lamps did you use? I suggest Daylight Deluxe fluorescent lamps which I'm sure didn't come with your shop light. 

Use yellow mesh to prevent UV light scatter but you won't see any real benefit with mesh counts under 200 lpi.

There is no real reference to your line thickness, but you should use a higher mesh count for fine lines. You have broken lines with small areas that are the first to go.

You are using a classic diazo emulsion which is not as fast as a modern SBQ emulsion that is pre-sensitized at the factory and has an 18 month shelf life. You have a low power light source. To compensate you need a faster exposing emulsion like Autotype Autosol 9000 or Ulano QTX.


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## aust1025 (Mar 1, 2007)

Can anyone tell me if halogen lights are ok?


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## RichardGreaves (Nov 7, 2006)

aust1025 said:


> Can anyone tell me if halogen lights are ok?


Most exposure units that use quartz/halgogen lamps are usually combined with fluorescent black lights because of the limited low-range UV output of the quartz bulb. (Quartz emits more white light than blue UV light.)

The scientific range of UV light that will exite stencil sensitizers is:
*
UVA* (400–320 nm) is also called Long Wave or "blacklight" and the most useful to screen makers. 99% of the ultraviolet radiation that reaches the Earth's surface is UVA which makes it an excellent light source. UVA is the least harmful, but can contribute to the aging of skin and cause skin cancer.

*UVB* (320–280 nm) is below the usual range that is useful to screen makers, but they often work. UVB does much more harm to skin than UVA.

A halogen lamp is a fused quartz glass tube (which can withstand high temperatures), filled with a tungsten filament and halogen gas. The hot filiment that emits light makes this an incandescent lamp.

A side effect of using high temperature quartz is that it will not filter UV-B light emited by the tungsten filiment. Ordinary glass stops these rays. It is the invisible UVB light that can cause eye damage and cross-link stencils.

Beware, some manufacturers add a coating of UV inhibitors on lamps destined for the home lighting market. When this is done, a halogen lamp with UV inhibitors will produce less UV than its standard incandescent counterpart. 

The lamp has to get hot to get the tungsten filiment to glow and the haogen gas counteracts the filiment evaporates when giving off light and is chemically re-deposited at the hot spots. 

Many household halogen lamps have an additional piece of safety glass to prevent fires, but they usually use ordinary glass, which, absorbs most of the UV-B light.

Quartz bulbs emit light more infrared light, which means quartz tube will produce more heat than other UV-output bulbs. UV light does not produce much heat, infrared light does. 

Sure. A halogen lamp is OK, but there are other lamps that are richer in UVA radiation like metal-halide. SOME fluorescent lamps (Daylight Deluxe) are very rich in UVA, but they have very little power so you have to keep them close to the stencil and packed them tight, to cover the stencil evenly with light. A major benefit to fluorescent lamps it that they are cool to the touch.


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## aust1025 (Mar 1, 2007)

i keep hearing about black lights, i have a real 2ft tube black light, will that work?
Otherwise i'll just stick with the fleurescent(sp). 

Thanks for the detailed info, it really did give me a better understanding.


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## RichardGreaves (Nov 7, 2006)

aust1025 said:


> i have a real 2ft tube black light, will that work?
> Otherwise i'll just stick with the fleurescent(sp).



At 6 inches it will cover an area 22" x 6". At 12" I don't think you will get much exposure power to cross-link your stencil. Use a very fast, sensitive SBQ emulsion.

How big is your image?


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## aust1025 (Mar 1, 2007)

well i have a bunch of orders i need to print, the largest one would be the front
print on a concert t-shirt its about 9" X 14" or so. 

Right now i am using a shop light resting on some milk crates with a storm window as the glass, the tubes are 40 watt soft white bulbs and i just cant get the exposure time down that way, so i have been using a screw in flood light with
a couple of peanut cans (about 3.5) inches to hold the light over the stencil.

I am worried that storm window may have that protective coating over it but cant really tell how old the window is.


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## RichardGreaves (Nov 7, 2006)

*Difference is between yellow mesh and white?*

Make some calls and find some: 

GE BL Black Light Bulbs

GE Daylight Deluxe F40DX


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## aust1025 (Mar 1, 2007)

Will do, thanks for all the help.


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## Bill Hood (Apr 11, 2007)

I am mostly in agreement with Richard, here. He is right on about the store windows and in fact all tempered glass will cause longer exposure times due the manufacturing process of tempering glass. I have actually been able to do some research on this as my shop was next door to a large glass company for many years and I had a great variety of glass at my disposal. Most store windows do have an invisible anti-UV coating applied to them.

I do disagree with the use of fluorescents bulbs with mesh counts above 110 as it is almost impossible to get detail on fine lines and halftones when using these types of bulbs. While the daylight lamps will give you a higher degree of UV exposure, they are still no better at stopping the great scattering of light that occurs when using more than a single light source.

I would suggest that a much better exposure unit than what is currently being used is the sun. Cut a piece of foam the same size as the inside of the screen. Place a piece of black material over the foam and insert into the squeegee side of the frame. Next, place a film positive onto the bottom of the screen, against the emulsion and cover with a piece of clear window pane glass. Carry this into the sunlight with one thumb positioned over the emulsion. It should only take about 20 - 30 seconds to expose on a bright day. Now, every five seconds quickly move your thumb off and back to the same spot. When you see a distinct difference between where your thumb has been and the emulsion that has received the full exposure, the screen should be exposed. This works on diazo, but not on pure polymer emulsions. But anyone who would probably spend the money on pure polymer emulsions would probably have a metal halide exposure unit.

Chromaline makes a great UV Minder device that will actually 'read' the sun and beep to let you know that the exposure has been reached no matter how overcast the sun. I think it is about $300 and is really a great tool to use as an integrator as well as for the purpose it was intended.

If you really are quite broke and need something besides the sun (maybe you only work at night?) then you can buy a quartz halogen work lamp with 2 500-watt bulbs. Put these, your choice, either on the floor or the ceiling at a distance equal to the diagonal of your frame size and voila you have a poor man's night time exposure unit.

Dyed fabrics help eliminate halation or the scattering of light during exposure, by absorbing the light rays.

Mesh fabrics are available in clear (or sometimes called white) yellow, orange, and red. Each of these colors performs a unique function. The clear or white mesh is used for those images with little or no detail. Yellow is the most common mesh color for mesh counts above 110 tpi. Orange is used by those printers who want a bit more detail and reputation. Red is used mainly by balloon printers looking for detail in the slightly inflated balloon so that when the balloons are completely inflated the detail will be quite good.

Contrary to what was stated earlier in the thread, each of the colors will require increased exposure times based upon the density of the color. As a rule, exposure times for fabrics of the same mesh count will increase as follows, with clear or white fabric as the reference:

Clear or White Mesh 100%
Yellow Mesh 125% of the Clear Exposure
Orange Mesh 150% of the Clear Exposure
Red Mesh 200% of the Clear Exposure


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## brs1 (Mar 16, 2008)

"Clear or White Mesh 100%
Yellow Mesh 125% of the Clear Exposure
Orange Mesh 150% of the Clear Exposure
Red Mesh 200% of the Clear Exposure"


Bill you appear to have in-depth knowledge, so it seems that yellow does not burn an image faster than the standard white mesh.

Thanks for the useful info all!

p.s. sorry about bringing back such an old thread


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## tpitman (Jul 30, 2007)

aust1025 said:


> i keep hearing about black lights, i have a real 2ft tube black light, will that work?
> Otherwise i'll just stick with the fleurescent(sp).
> 
> Thanks for the detailed info, it really did give me a better understanding.


If that real 2 ft. bulb is one of the purple ones you use for your fluorescent posters when you're stoned, the answer is no (or not very well). The unfiltered blacklights you would use look just like a normal white fluorescent bulb.


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