# How long I need to burn my screens



## etshirt (May 8, 2008)

Hi

I just got a new vastex e1000 exposure unit. It works with 4 - 24" black UV bulbs.

I burned my first screen for 7 mins and part of the image came out. I burned a second screen for 10 minutes and even more design came out, I could pell the emaulsion of with my hands.

Can someone please help I dont want to wasted more screen.

My screen where brand new, did I have to wash them or degrease them first?

I also use diaxo green emulsion pro I coated the screen twice in the outside and once inside did I do it right?

Greg


----------



## RichardGreaves (Nov 7, 2006)

*Measuring exposure*

*Measuring Stencil Hardness*
You will get diazo color change with your stencil, but without a step wedge test positive, you can't really tell if you actually cross-linked all diazo the sensitizer.

PositiveDave posted an article showing how to make a free stepped exposure test, but you sacrifice a screen just to make each test.
http://www.t-shirtforums.com/t-shirt-articles/t106506.html

"Classic Exposure Step Test Video 4Mb 4 minutes (http://www.ulano.com/video/UlanoExposureTest.256k.wmv)

Stencils with diazo sensitizer will have a color change because the 'yellowish' diazo will actually decay and the stencil will return to the color is was before you sensitized it.

For the best durability, look at the section where you don’t see any difference between your stepped exposures and the completely exposed area. This means the stencil reached it's saturation point, and more UV energy just doesn't change it any more. Don’t waste time exposing it if it won't change any more.

*Manual Stepped Exposure video*
Support Menu of Screen Making Products

When you get bored with all those steps, on a screen you can't print, I suggest using a US$10 Stouffer T-2115 21 step gray scale to simulate 21 different exposures. A Stouffer scale is a 5 inch film positive with darker and darker filters next to each other in steps. This is a standard photographic darkroom test positive that's been used since the 1930's.








Properly used it should last a lifetime, so I want you to put it every screen you expose for the rest of your life. It's visual feedback you exposed the stencil properly.

Transmission Step Wedges

When you develop the stencil, areas that didn’t get enough exposure will dissolve with water and rinse down the drain. Aim for a minimum of a *Solid Step 7* that adheres to the mesh and survives development. More exposure will make your stencil more durable and less will make the stencil less durable, but light scatter could start to choke fine lines or halftones.


----------

