[naten96]

Hello to you all and thank you in advance for any help or input

Well I built my own exposure unit using the following

-8 20w unfiltered black lights
-30 x 36 box
-30 x 36 (1/4" thick glass)
-top of bulb sit approx. 6" away from the glass.

Now as far as emulsion im using ulano 925wr ; coating once each side letting it sit over night then come back a day or two later. taping transparency covering with dark blanket putting some weight on the screen im exposing for 4min ive tried 3min and 5min also but for some reason the thin parts don't come off as easy (design is just font) and im having to use regular water hose pressure to remove uncured emulsion having a hard time getting the timing right can it be ?? should I use pressure washer when doing this ??? any input is highly appreciated .

 

[sben763]

https://www.youtube.com/results?search_query=sben7633&sm=12 checkout videos washout and IMG1754. I did these for other members as a guide. you don't have to scrub it just makes it quicker and on the shirt side I use no pressure . The ink side can take more abuse. That's diazo emulsion and a similar exposure unit I use to have I think was about 4-6 min depending on mesh. A few things it can be. Bad emulsion or improperly handled emulsion. Bad films. tape a coin to the screen on your next test. if it washes out but the image doesn't most likely a film problem. If the coin area doesn't them likely a emulsion problem. Make sure you have the back side on the screen is covered during exposure and the screen is handled in light safe environment from coating to washout. If UV hits it any other time then exposure you will have problems

 

[ironhog]

Get an exposure strip and use it to dial in your times. Without one you are shooting in the dark.

 

[20vK]

Sean - did you mean to say the ink side can take more abuse? The side that is on the same side as the light source will form the strongest cross-links.

You can also try a step test with a piece of thick card.

But follow Sean's link and advice with the coin. You need to know if it is emulsion or positive first. Take things logically and slowly cancel out possible problems.

For diazo emulsion, my exposure times ranges from 6 minutes through to 45, depending on light source.

 

[mnweck]

I have a homebuilt unit with 6 of the unfiltered black lights. I get good exposures at 6 1/2 minutes. I am using a black t-shirt/foam/weight. But as has been said, step wedge calculator. hope that helps.

 

[naten96]

Thanks fellas for the input I just reclaimed my screens and gonna do my second run for the burns hopefully I get much better results using some of these techniques

 

[sben763]

Sean - did you mean to say the ink side can take more abuse? The side that is on the same side as the light source will form the strongest cross-links.

Yes I did if its properly exposed. If you scrub the front too hard it will create scratches ruining the gasket of your stencil.

 

[20vK]

I see what you mean. I thought you were referring to actual emulsion hardness