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LMB9888 · April 24th, 2009

When printing white I have been told and seen the process of coating the outside of the screen twice and sometime 3 times to get a better quality white prints.

I use CCI DXP Diazo Photopolymer dual cure and was wondering what the burn time for a 2 coat outside and one coat inside and a 3 coat outside and 2 coat inside. I use a 500 watt hologen bulb when burning. Thanks

out da box · April 24th, 2009

Longer, but only a step wedge or exposure calculator or my favorite- trial and error- will tell you what YOUR time is.

RichardGreaves · April 24th, 2009

Screen makers don't really coat - we scrape. Mesh has holes in it, so maybe emulsion ends up on the other side!

Start coating on the bottom of the screen until you see the emulsion link up on the other side and form a shiny gloss coating.

If you don't fill the holes, when you turn the frame and make final coats from the inside of the screen, air will get trapped in the holes that are now like bubbles, reducing the amount of emulsion in the holes as the water evaporates. A diazo dual cure like DXP will be about 40% solids, so that means it is 60% water. When it dries the liquid coating will flow downward with gravity a shrink- taking on the shape of the mesh. That coating ends up looking like a waffle when it's dry.

Face coats on the dried coating can be used to fill the dimples in the surface. Capillary film will give you an instant film on the bottom of your mesh.

You forgot to tell us what mesh you are using,(mesh is the primary meter of ink deposit, not coating), mesh tension, (tighter is better) and if you are coating with a 2mm or .5 mm trough lip.
Coating FAQ of Screen Making Products

'midwaste' has told us he exposes a dual cure with a 500 watt halogen lamp for 12 minutes at 20 inches with the UV safety glass removed, but I want you to buy a $10 Stouffer 21 Step Gray Scale and learn to measure exposure.
Exposure FAQ Screen Making Products how to measure exposure

Search these forums for 'halogen' and you will find hundreds of posts to study.

InkedApparel · April 24th, 2009

I use the same exact emulsion....the pink stuff. and a 500 watt halogen 16 inches off screen..I burn my screens for 23 minutes and use a 21 step wedge and get a solid 7 every time...with that said...everyone "scrapes" there screens differently...I do a 1/1 and use a 110 mesh for white..and most of the time I can get a nice opaque white with 1 pass.but without a step wedge .....trial and error is all you have. Hope this helps

Inked

midwaste · April 27th, 2009

It takes me 18 minutes to expose QX-1 with a 500W at 20" to expose to a solid 7 step.

I also use Richards technique of coating, coating shirt side with round edge until its fully glossy on the squeegee side, then flipping and using sharp edge to push the emulsion back through to the shirt side.

LMB9888 · April 27th, 2009

Thanks for all the imput everyone.

aust1025 · April 28th, 2009

We have an exposure unit with 12 purple light bulbs, we coat our screens with 3 on the outside and 2 inside, burn times (for a 110) are between 38 and 42 seconds.

veedub3 · April 29th, 2009

Quote:

Originally Posted by LMB9888


	When printing white I have been told and seen the process of coating the outside of the screen twice and sometime 3 times to get a better quality white prints.

I think that may be based on individual results as I have never needed to make more than a 1/1 pass with emulsion when printing white plastisol. (Hell any color for that matter) Also I use a CHX-7500 Emulsion and Extreme White and the prints are crisp with only one pass.

I think it may have more to do with your Exposure set up more so than anything.

Veedub3

out da box · April 29th, 2009

I have yet to get a solid, opaque white on my auto with one pass. 2 passes on 110 mesh- not really opaque.
Tomorrow I'm going to see how some 110's I coated today work out. I got a much thicker emulsion buildup on this last set of screens. I think the thicker deposit will help me get a bright white underbase or opaque solid area.

InkedApparel · April 29th, 2009

for a white underbase I coat the shirt side of the screen twice and the squeegee side once...and get nice opaque whites with one pass....

Inked

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