Combined with the ambient temp and possible humidity level. I have a dryer box and dry at 80-95F my box doesn't had a dehumidifier but I run one by the box air inlet. Before the dryer box I would use a small ceramic heater and a box fan on low not directly at the screen. Every time I don't run the dehumidifier I have blow outs.
Saati 21 Step Sensitivity Guide and Emulsion
2
Hi, all.
I began to burn 110 screens using CCI ProChem DC-Plus emulsion. I'm using a SAATI 21 step guide to find the correct exposure for my screens. I have a new Ranar CBX 2024 exposure unit.
My question, why did my stencil completely blow out on the image (and registration marks) when exposing for 12 minutes? (I have no picture of this screen as I reclaimed it right away.)
My first test was done at 8 minutes (see image below):
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then I did a 10 minute test:
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On both these screens the image (art) came out fine, with the first (8 min.) being a bit sharper. Registration marks were also good and sharp on the 8 minute exposure.
According to SAATI, and on my first exposure, I had to increase my exposure time by 1.4x, increase one step. 8 x 1.4=12.2, this gave me ~11 mins. and 20 secs.
But, when I burned the screen at 12 minutes, the art (and reg marks) washed out completely.
Process in washing out: rinsed the print side first, then the squeegee (ink) side. I let sit for about 45 secs. then used pressure washer (not hard sharp pressure, but flat pressure) at about 3 feet distance. **This was done to the 12 min screen. For the 8 and 10 min screens, I used a nozzle (the one most use.)
I did use bottled water to mix diazzo(sp) and let mixed emulsion sit for 1 30mins. Did a two-one emulsion coating. All processes were done under yellow lights. Ambient temp was in the mid to low 60s.
One thing, I did not use a fan to dry out my screens upon coating. I did leave them to dry for 24 hrs in my Ranar job rack, ink side up, fully covered from light. But, it did rain overnight and my rack is inside a large tent that's enclosed.
Could my inconsistency with washout be due to emulsion not fully dried? I did not feel any wet spots upon inspection, before exposing.
Thank you, in advance, for any insight.
Joey
I began to burn 110 screens using CCI ProChem DC-Plus emulsion. I'm using a SAATI 21 step guide to find the correct exposure for my screens. I have a new Ranar CBX 2024 exposure unit.
My question, why did my stencil completely blow out on the image (and registration marks) when exposing for 12 minutes? (I have no picture of this screen as I reclaimed it right away.)
My first test was done at 8 minutes (see image below):
then I did a 10 minute test:
On both these screens the image (art) came out fine, with the first (8 min.) being a bit sharper. Registration marks were also good and sharp on the 8 minute exposure.
According to SAATI, and on my first exposure, I had to increase my exposure time by 1.4x, increase one step. 8 x 1.4=12.2, this gave me ~11 mins. and 20 secs.
But, when I burned the screen at 12 minutes, the art (and reg marks) washed out completely.
Process in washing out: rinsed the print side first, then the squeegee (ink) side. I let sit for about 45 secs. then used pressure washer (not hard sharp pressure, but flat pressure) at about 3 feet distance. **This was done to the 12 min screen. For the 8 and 10 min screens, I used a nozzle (the one most use.)
I did use bottled water to mix diazzo(sp) and let mixed emulsion sit for 1 30mins. Did a two-one emulsion coating. All processes were done under yellow lights. Ambient temp was in the mid to low 60s.
One thing, I did not use a fan to dry out my screens upon coating. I did leave them to dry for 24 hrs in my Ranar job rack, ink side up, fully covered from light. But, it did rain overnight and my rack is inside a large tent that's enclosed.
Could my inconsistency with washout be due to emulsion not fully dried? I did not feel any wet spots upon inspection, before exposing.
Thank you, in advance, for any insight.
Joey
1 - 9 of 9 Posts
The industry standard for stencil hardness is a Solid Step 7.
![]()
On a 21 Step Scale, (Saati's is made by Stouffer) the numbers are open, so a Solid Step means the number disappears, which means, none of the surrounding stencil dissolved.
Lighter colored patches means some of the underexposed stencil on the inside of the screen has dissolved.
Your 8 minute picture is a Solid Step 2.
Your 10 minute picture is also a Solid Step 2.
Under exposure
It's the job of the screen maker to completely harden the stencil so it survives. If your stencil doesn't survive washout, you don't need Saati to tell you, you're under exposed.
If you're printing plastisol and your stencil doesn't get to a Solid Step 7, you really don't have any problems.
Plastisol ink is like salad dressing when it comes to attacking a stencil, but water-based ink, (made of 80% water) is made of the stuff that dissolves un-cured stencil like the Wicked Witch of the West.
On a 21 Step Scale, (Saati's is made by Stouffer) the numbers are open, so a Solid Step means the number disappears, which means, none of the surrounding stencil dissolved.
Lighter colored patches means some of the underexposed stencil on the inside of the screen has dissolved.
Your 8 minute picture is a Solid Step 2.
Your 10 minute picture is also a Solid Step 2.
Under exposure
It's the job of the screen maker to completely harden the stencil so it survives. If your stencil doesn't survive washout, you don't need Saati to tell you, you're under exposed.
If you're printing plastisol and your stencil doesn't get to a Solid Step 7, you really don't have any problems.
Plastisol ink is like salad dressing when it comes to attacking a stencil, but water-based ink, (made of 80% water) is made of the stuff that dissolves un-cured stencil like the Wicked Witch of the West.
Wow, thank you for including a visual example of the test strip, I could not find a single one online! The directions from Saati are lacking.The industry standard for stencil hardness is a Solid Step 7.
![]()
On a 21 Step Scale, (Saati's is made by Stouffer) the numbers are open, so a Solid Step means the number disappears, which means, none of the surrounding stencil dissolved.
Lighter colored patches means some of the underexposed stencil on the inside of the screen has dissolved.
Your 8 minute picture is a Solid Step 2.
Your 10 minute picture is also a Solid Step 2.
Under exposure
It's the job of the screen maker to completely harden the stencil so it survives. If your stencil doesn't survive washout, you don't need Saati to tell you, you're under exposed.
If you're printing plastisol and your stencil doesn't get to a Solid Step 7, you really don't have any problems.
Plastisol ink is like salad dressing when it comes to attacking a stencil, but water-based ink, (made of 80% water) is made of the stuff that dissolves un-cured stencil like the Wicked Witch of the West.
I burned three screens last night and all came out great. On the first test (13 minutes), the test strip was solid at 8. On the other two tests, which I let expose to 11 minutes, the test strip came out to a 80-90 percent solid 7. I was very happy with that time as my screens washed out fast. The art detail and edges were very sharp.
I believe that my problem with my first test exposures was that the emulsion wasn't dry enough on the screens. No matter what times I used, I was still going to have problems. Even though they did seem dry, they were not. This time, I kept them dry for three days- no rain either.
Now, I see how important it is to dry screens in optimal conditions. In my situation, I will have to buy or build my own drying unit. Unfortunatey, it's the equipment I least gave attention to.
1 - 9 of 9 Posts
