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aust1025 · March 2nd, 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...

aust1025 · March 2nd, 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

Don276 · March 2nd, 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.

Fluid · March 2nd, 2007

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

aust1025 · March 2nd, 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?

aust1025 · March 2nd, 2007

my screen is a white mesh at 155 count.

Fluid · March 2nd, 2007

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.

aust1025 · March 2nd, 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.

aust1025 · March 2nd, 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.

Fluid · March 2nd, 2007

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

aust1025 · March 2nd, 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?

Fluid · March 2nd, 2007

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.

aust1025 · March 3rd, 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

Oritron · March 9th, 2007

Quote:

Originally Posted by aust1025


	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.

RichardGreaves · March 15th, 2007

Quote:

Originally Posted by aust1025


	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.