# Exposed Screen Not Washing Out.



## csok (Nov 5, 2008)

I just built a Pulse Start Metal Halide 1000 watt 10k vacuum unit. 

The light source is about 25" from the glass. 

It's a cool tube fixture with a 6" inline fan. Thinking that this was adequate, I didn't put a fan in the main cabinet, just the cool tube.

After what I have read I think it may be a cabinet/glass heat issue, but I want an expert opinion. 

*The film positive was sticking to the emulsion slightly after all these burns. Is this normal?*

Here are the details.

I am using:

Murakami Photocure Blu. 
Coating with round edge 2:1
using a SAATIprint 21 step guide

I had a successful exposure on 160 mesh at 3:00 but it was only a solid step 6 now that I look again. It gets weird after this....

So, I burn 3 x 110's - 1st for 3:40, way over, 
(dont follow the guide but drop it to what was successfull on 160) 
burn for 3:00, still 3 steps too much. 
Burn for 2:06 like the guide says and I get a solid step 7 
(I think I was too hard and washed it down to 6) 
but some of my art doesn't wash out. 
I tried to wash it out for about 5:00

Thanks for the advice,
Chad


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## Printor (Apr 16, 2015)

The gauges are nice if your film is output at the same perfect quality the gauge was. that's rare. some times it's more useful to design your own gauge and print it with your film printer, since that's what you really have to work with. If your film isn't perfect, I'd go old school and under expose it until it falls apart, and go up from there.


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## Printor (Apr 16, 2015)

Also I cant tell how big that image is from the pics it might need a 150-160 if your coat is thick.


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## csok (Nov 5, 2008)

Printor said:


> The gauges are nice if your film is output at the same perfect quality the gauge was. that's rare. some times it's more useful to design your own gauge and print it with your film printer, since that's what you really have to work with. If your film isn't perfect, I'd go old school and under expose it until it falls apart, and go up from there.


That's a good point! My films have a frosted look.


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## sben763 (May 17, 2009)

Something isn't right. What kind of glass. With chroma blue and that bulb, if it's the one I recomended you should be way under 1:00. Also what's your humidity. Get a cheap weather station with a remote sensor. I know what humidity is in shop vs the dry box. Usally sticking is due to the stencil still being too moist. It also can be heat but at 25" shouldn't be a issue. 

If your above 40% it's humidity and will retard the exposure. So 1 screen if it's dry 40% or lower will expose much faster then one that's at 50% humidity. 

Photopolymer emulsion will even reassorb moisture. Diazo will also but not easily.


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## Printor (Apr 16, 2015)

Aterthought, do you use a pressure washer or hose to rinse your screens after burning.


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## csok (Nov 5, 2008)

sben763 said:


> Something isn't right. What kind of glass. With chroma blue and that bulb, if it's the one I recomended you should be way under 1:00. Also what's your humidity. Get a cheap weather station with a remote sensor. I know what humidity is in shop vs the dry box. Usally sticking is due to the stencil still being too moist. It also can be heat but at 25" shouldn't be a issue.
> 
> If your above 40% it's humidity and will retard the exposure. So 1 screen if it's dry 40% or lower will expose much faster then one that's at 50% humidity.
> 
> Photopolymer emulsion will even reassorb moisture. Diazo will also but not easily.


I got the glass used at Habitat for Humanity. I have no idea what the iron content would be. 

It's the MH 1000w 10k you recommended. 

My shop is in the basement. 
The dehumidifier is sitting in the closet with no external drain.
I haven't even checked the humidity level. 
I just assumed that after 24 hours it would be dry. 

My money is on the humidity level, especially if the photo-polymer emulsion is capable of re-absorbing moisture. 

Thank You for the response Sean!!


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## csok (Nov 5, 2008)

Printor said:


> Aterthought, do you use a pressure washer or hose to rinse your screens after burning.


I am using a hose with a mist and flat spray. I think it may be the humidity level.


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## csok (Nov 5, 2008)

My glass has the green tint which is indicative of a higher iron content. So, I will get my humidity under control and order another piece of glass.


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## sben763 (May 17, 2009)

PPG starphire.


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## Printor (Apr 16, 2015)

Those screens look like you could have got them with a pressure washer. If your using less than perfect film, you can often over expose a little and rinse with presure. While your fine tuning everything else, you should get a cheap home $100 pressure washer, use the weakest fan tip it comes with, from a distance (2-3') you need one for reclaiming any way. It will take some practice but once you get use to it, you will always do it that way.


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## csok (Nov 5, 2008)

sben763 (Sean) I owe you a beer, or a T-shirt!

I burned a successful 110 mesh screen at 1:00 and held all my fine detail. 

The humidity was definitely the issue! 

The soda glass does not appear to be affecting time enough for me to change, and because it only cost me $20, I think I will stick with it for now.


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