[altereddezignz]

OK here is an issue that i am having. I use Ulano 925WR. I like the emulsion, cover's good. Last a long time. But for some reason i cured a 109 screen the same as i always do. My image is simple 3 big letters each letter having the a different animal print inside. Well 2 of the letters came out fine for the most part with the outline being good. The other letter the line is waivy almost like it did not completely cure. Also one spot were there is a little area in between the outline and the animal print it did not want to wash out. I wish i would have taken pictures but i cleaned the screen before i though about it.

And when i washed out the screen some of the emulsion stayed really stickey and i wiped a little off with my fingure down at the bottom of the screen.

I did a 1/1 coat and it was in a 6x8 room with a large heat exchanger dehumidifier for about 9-10 hours..

 

[altereddezignz]

Oh i am using a home built exposure table with f20t12 bulbs spaced 2 inches between each bulb and about 4-5 inches from the glass. curing for about 5 minutes.

 

[Naptime]

what kind of bulb?

uv, plain florescent, etc...

how long are you curing for?

 

[altereddezignz]

Sorry they are unfiltered UV bulbs.

 

[altereddezignz]

about 5 min

 

[geniussuineg]

maybe not enough positive contact. the more detail in a design the more pressure you need holding down the screen to the positive image. the pressure needs to be even as possible (this is the hard part) or one part of the image will expose more than another part of the image. I know I have a homemade unit. More (even) positive contact with image and screen; burn a little longer. If you emulsion is slimy then, it is under exposed.

 

[sben763]

If when you wet down the screen it's slimy that's a indication of under curing. How far are you bulbs from screen. And how many bulbs.

 

[lben]

I let my screens sit overnight to dry. When I burn them I have a 2" foam pad glued to an old cabinet door that I fit inside of the screen frame, then I put 6 heavy containers like gallon jugs and paint cans on top of it to force the screen onto the film evenly. I have wooden screens so there is always the possibility of a warped frame. This process takes that out of the equation. Then I burn for 5 - 8 minutes depending on my emulsion and which exposure unit I'm using.

 

[altereddezignz]

I have wooden screens to and is was a 109 screen. There is about 5 inches if I remember right from glass to edge of bulb. As far as positive contact use a pc of 3/4 MDf that is cut to half inch inside diameter of the screen. I then out a full 5 gal pail of paint on top of it. So about 25-30 pounds. The only other screen I did on this table since I have built it was a 255 mesh and it was fine at 5 min. This is a brewer larger table than my last built exactly the same and I could expose low mesh screens with. I problem at 5 min. Guess I need to do a step test on all my screens again. I really need to order some new screens these are rather old anyways.

 

[equipmentzone]

OK here is an issue that i am having. I use Ulano 925WR. I like the emulsion, cover's good. Last a long time. But for some reason i cured a 109 screen the same as i always do. My image is simple 3 big letters each letter having the a different animal print inside. Well 2 of the letters came out fine for the most part with the outline being good. The other letter the line is waivy almost like it did not completely cure. Also one spot were there is a little area in between the outline and the animal print it did not want to wash out. I wish i would have taken pictures but i cleaned the screen before i though about it.

And when i washed out the screen some of the emulsion stayed really stickey and i wiped a little off with my fingure down at the bottom of the screen.

I did a 1/1 coat and it was in a 6x8 room with a large heat exchanger dehumidifier for about 9-10 hours..

Check your film positive and see if all the black parts are equally opaque.


Harry
Equipment Zone

 

[altereddezignz]

Oh yes very very dark to the point were nearly to no light at all is able to pass through the vellum.

 

[sben763]

Using velum instead of film will increase exposure time. Also velum deflects light in multiple directions thus on detail can cause 1 area to be under exposed while a 2nd area to over expose while a 3rd area to be perfect. Velum does work well for spot color designs with larger areas.

 

[altereddezignz]

Sorry it is transparent film. Didn't mean for that to be misleading. I just. Orally refer to it as vellum. When I am talking to someone about shirts and I say that I'll try as print there design on film tonight they always reply huh? You mean you are heat pressing my shirts no screen printing. That's not what I want. So it's easier for me to refer to it as vellum rather than film. Sorry for the long explanation.

 

[sben763]

Ok. I would mix you emulsion let stand for a few hours. Coat a new screen a do a step wedge test. This will give you some insight. I just looked and I originally thought you had a premixed pure photopolymer. You have diazo dual cure. Yes it usally will last a long time. I would buy only what you need for 3 months at a time. Ulano only gives it 6 weeks after mixing which is usally rediculous and will last mush longer but when using dual cure and you start to problems it usally best to get a fresh quart and eliminate as a problem. Also as unfiltered BL get older(even new this can happen) and if temps where you are exposing screens a lower than 65 I would turn on your bulbs for 5 min to prewarm bulbs. Then expose. If you turn on and you see the the gas dancing in the tube it is likely you need to prewarm them. You will get uneven exposure if not. I had this happen about 4 years ago so now when temps are cooler I always pre warm just to eliminate a potential problem

 

[altereddezignz]

Well I just got back from coating a 150 mesh screen. Used the same emulsion and used the same film that I used on the other screen. But this time I cured for 5min 30 seconds and all was well washed out great and have evn straight lines. I'll still do a step test but don't have time at the moment

 

[sben763]

Good deal. When your cured the last one maybe the humidity was a little high. Sometimes it's hard to figure out what happened. or the emulsion is on its way out.

 

[RichardGreaves]

The purpose of UV exposure is to change the stencil from something that will dissolve with water, into something that won't dissolve or breakdown with water. Stickiness is a symptom of dissolving, just like a postage stamp.

If the stencil breaks down - it's under exposed.

If the image area is hard to dissolve, UV energy leaked through your positive & 'crusted' it.