Emulsion - Mass Confusion

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cromaclothingco
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Emulsion - Mass Confusion

Post by cromaclothingco »

Before I ask my question I'd like to say that I have been reading this forum the last few weeks and I am amazed at how helpful everyone is here!

What I am using:

Light table

http://www.silkscreeningsupplies.com/si ... ct/RXP2536

Emulsion:
Murakami One Pot Sol C - SBQ pure photopolymer

Stencil
vector art printed from a laser printer on caseys page mill vellum - even added spray toner

The first emulsion I started using was the one I got from ryonet, the CCI DXP dual diazo and I have noticed that it worked much better on my exposure unit than the murakami one pot. But I switched from it because it didn't hold very fine detail real well, and a local print shop said that the one pot was amazing (they use the sun to burn). So I called murakami and talked to someone very knowledgeable and he said that the one pot is one of the more difficult emulsions and was not necessary for my application. So he recommended me their new emulsion - photocure pro. But, in the mean time I have a very expensive gallon of the one pot and in desperate need of a clean stencil.

I did two step wedge tests for 30 second increments - the first screen 30 seconds - 3 minutes and 30 seconds. The second screen for 3 min 30 till 7 minutes. The amazing thing is that the wedge tests are the only stencils I can get to come out that don't have "scum." The first wedge test had a lot of unexposed area that just came right out and it started to hold together better around 3 minutes 30 seconds. The second screen with more time, every increment looks fairly suitable. But i go with 4 minutes 30 seconds. But, still, no matter what I do the scum stays in my design, and if i pressure wash it any longer ( even with a hose with simple pressure attachment ) my edges start falling off. My water is ice cold - does this make a difference?

I rinse the first side with less pressure, then the back side, let it sit for about 25 seconds, then I spray the front side with pressure washer, then spray the back side with pressure washer, then try to finish off on the front side. But theres still a lot of scum inside the design and the detail is coming apart. I am on a 156 white mesh screen and my design has a fairly good amount of detail, but nothing extremely small.

The new emulsion that is soon to arrive - the photocure pro, says it only is good for 3 weeks after mixing in the sensitizer. Is there a way I can just sensitize a portion of it and not a whole gallon?

Thanks for any help in advance!

Matt
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Post by ROADSIDE »

Well.... a step wedge is usually done using 1 screen from the way I was taught.

I like the Kiwo Poly Plus-S Dyed emulsion.
but then again... it has its moments.

I would try a lower mesh count... like 110.

What LPI and DPI are you using on the film?

Can you scan your film into the computer and post it for us to see?

I am guessing the FILM and the SCREEN are what are causing the problem and not the emulsion.
.... I can give you my opinion but I can't tell you if it's right or not.
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Post by cromaclothingco »

Well, seeing that the film has worked before on other emulsions (and the wedge tests, printed on same paper, were scum-less), I think it might be the way I have coated my screens... would more than 1 coat be beneficial?

also - The new emulsion that is soon to arrive - the photocure pro, says it only is good for 3 weeks after mixing in the sensitizer. Is there a way I can just sensitize a portion of it and not a whole gallon?

also, i do not have a scanner, but the designs were printed from a local shop for me using their printer and paper
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Post by yaleteamsandtees »

Are you using the included foam pad or a vacuum blanket?

Either way, Place a piece of black construction paper
on top of the image area on the screen then put foam on.

Are you weighting the foam down with anything?

Sounds like you're getting light leaks from above
slightly exposing the image area.

This would also explain the feathered edges of the emulsion.

Our old vac table had a natural rubber blanket and we
had to cover the inside of the screen with black cardboard.

We now have a black blanket and no need to cover.
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Post by ROADSIDE »

I would say trying to sensitize a portion of the gallon will be difficult because you need to get the ratio pretty exact.


100% yes more then 1 coat is needed.....

The way i do it is as follows:
1 coat on the bottom then 2 coats on the top, then a scoop on the bottom to remove to much excess.
put the screen in a rack in your dark room to let it dry.
If you dont have a rack or a dark room simulate it somehow.

Every good screen printer needs a scanner, :P

T
.... I can give you my opinion but I can't tell you if it's right or not.
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Post by cromaclothingco »

yaleteamsandtees wrote:Are you using the included foam pad or a vacuum blanket?

Either way, Place a piece of black construction paper
on top of the image area on the screen then put foam on.

Are you weighting the foam down with anything?
Yes, I am using the foam insert with a piece of wood over the top with 5 gallon buckets weighing it down. But, you're saying to put a piece of black construction paper between the inside of the screen (ink side) and the foam? This is something I have not yet tried.


Also, could you clarify which side you are referring to as top and bottom - and I have a heated drying cabinet that I built that is light safe and completely dries the screens in about an hour.

Thanks again for the help!
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Post by cromaclothingco »

And another thought - I think I might be coating my screens at an incorrect angle, is there a suggested angle, because the way I am doing it now, seems fairly steep. The correct angle helps to get the correct mil thick, consistently, right?
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Post by yaleteamsandtees »

Top and bottom would be as viewed on the press.

Top=ink side
Bottom=shirt side

How hot does your drying cabinet get?

Anything over 105 degrees can start to cause problems.

You also may have too much weight causing the glass to bow
and the film to lose contact.
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Post by cromaclothingco »

the drying cabinet definitely doesn't get that hot, it stays right around 80 degrees. I will try what you guys have suggested and post an update

:D
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Post by ROADSIDE »

Croma... Where are you located?
Just curious...
Last edited by ROADSIDE on Sat Feb 09, 2008 12:46 am, edited 1 time in total.
.... I can give you my opinion but I can't tell you if it's right or not.
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Post by cromaclothingco »

ROADSIDE wrote:Croma... Where are you looked?
Just curious...
I am guessing that you are asking me where I am located - Northern California

:wink:
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Post by cromaclothingco »

Hey I have about 5 screens sitting in my rack that are already dry with 1 coat of emulsion on each side, can I just add another coat to those screens or is it better to put all the coats on at once?
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Post by raystepone »

Just wanted to weigh in. I use DUAL DIAZO from ryonet i have not had any problems with it at all.It last for about three to four months[ depending on cond.] Is the reason you switched due to cost if not , consider going back.
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Post by yaleteamsandtees »

cromaclothingco wrote:Hey I have about 5 screens sitting in my rack that are already dry with 1 coat of emulsion on each side, can I just add another coat to those screens or is it better to put all the coats on at once?
The proper technique is to wait between coats.
If you don't, you're not applying additional coats,
you're just moving wet emulsion bac and forth.

How would it build up in thickness??

It's kinda like dipping candles.
Each dip adds a layer of wax.
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Post by ROADSIDE »

Am I the only one that keeps my emulsion in the fridge?
Keeps it from being to loose and drippy
.... I can give you my opinion but I can't tell you if it's right or not.
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Post by yaleteamsandtees »

Nope. We do it too.

The stuff we are using now is a lot thicker
than most we have used.

It also prolongs the shelf life.
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Post by cromaclothingco »

yaleteamsandtees wrote:
The proper technique is to wait between coats.
If you don't, you're not applying additional coats,
you're just moving wet emulsion bac and forth.

How would it build up in thickness??

It's kinda like dipping candles.
Each dip adds a layer of wax.

Yeah thats what I assumed, but the way he stated it --
1 coat on the bottom then 2 coats on the top, then a scoop on the bottom to remove to much excess.
-- made me think that it was to be done all at once.

But, you said that refrigerating the emulsion will increase its lifespan. What kind of increase are we talking about? If there is any way I can make this emulsion last more then three weeks I'm interested!

Thanks for all the help so far :)
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Post by ROADSIDE »

cromaclothingco wrote:
yaleteamsandtees wrote:
The proper technique is to wait between coats.
If you don't, you're not applying additional coats,
you're just moving wet emulsion bac and forth.

How would it build up in thickness??

It's kinda like dipping candles.
Each dip adds a layer of wax.
Yeah thats what I assumed, but the way he stated it --
1 coat on the bottom then 2 coats on the top, then a scoop on the bottom to remove to much excess.
-- made me think that it was to be done all at once.
I do it all at once and rarely if ever put a second coat after drying.
The reason for doing it the way I said... is to ensure the emulsion is worked into the screen good enough.... Leaving extra on the top helps with build up because when you put it in the rack... GRAVITY does the rest.
I am not saying YALE is wrong at all. Just stating way I do what I do.
.... I can give you my opinion but I can't tell you if it's right or not.
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Post by yaleteamsandtees »

Our first coating goes like this.

Start on ink side, push emulsion
thru to shirt side.

Turn screen around and push emulsion
back thru to ink side.

Turn around and push back to shirt side and dry in rack
shirt side down.

When dry, coat shirt side one more time.

Dry shirt side down.

Whatever seems to work for you. :wink:

That's just the way I learned it many moons ago.

-Rob
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Post by cromaclothingco »

So finally today I get to conduct another step test with the new emulsion.

I talked to the technical guy at Murakami and he told me to coat my screens like so - using the rounded edge of coater - bottom one coat, top two coats, all at once.

So I coat three screens and after they dry it looks as if only 1 of them is usable. The others are really wavy and the emulsion looks like it is thicker in spots then others.

The screen, which should be dry it has been in the drying cabinet for close to two days, with mild mild hot air circulating. But, I go to test it and I do exactly as the Murakami guy suggests, from 3 minutes to 6 minutes. Then I go to wash it out (not using pressure washer) and I notice a lot of suds, a lot more than I have ever seen come off. None of it is holding together, the crosshatching in the test looks okay around 3 minutes, but is falling apart in random places all over the time spread. All of the numbers washed off and nothing was really legible or clean on the whole screen. So i walk away and come back in 10 minutes and notice that the emulsion looks really weird at this point. Almost like cracks you would see out in a dry river bed. Just random cracks all over.

HELP - are the screens not completely dry? Am I not applying enough pressure when I coat them? Does adding coats add a considerable amount of time to the exposure?
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Post by TheGraphicsFactory »

As in all problems, you must control the variables. And make ONE change at a time when you are try to solve the problem. Otherwise, you have "chaos".

There are lots of different types of emulsions and many brands. First ensure that your emulsion is compatible with the type of ink you are printing with...water base, plastisol, vinyl, oil base, etc. Next, regardless of brands, types of emulsions are similar. There are primarily diazo and photopolymers, or some combination. Generally, photopolymers are very fast exposing, while the diazo is slower. If you have to store your emulsion in the fridge, it is a diazo. Photopolymers do not require refrigeration. However, when mixed, they all have a shelf life. Diazo is cheaper, and often sold with kits for hobbyists. One factor that distinguishes one emulsion from another, is its durability. The more expensive emulsions will last longer. Compare tens of thousands of strokes compared to a thousand.

Make sure you mix properly and according to instructions! Stir thoroughly, but gently. Try to avoid air bubbles. It is recommended to work in a light safe room, under yellow light (does not need to be totally dark). Allow the newly mixed emulsion to set OVER NIGHT before you use(even though some say wait only fifteen minutes).

Use a screen coater (looks like a trough)! Avoid using cardboard. Pour the emulsion into the coater until it is filled about half way and let it level out. Pick up the coater with your dominant hand (right if you are right handed) so that the "sharper" edge will touch the screen. While holding the top of the screen, stand it on a table so that the "edge" of the screen is towards you (not the mesh)...now comes the technical stuff.

The number of coats, and how you coat depends on the mesh count. Low mesh counts (below 86), usually get 4 coats. Higher mesh counts (including, but sometimes above 160) only get 2. Everything in between gets 3. Very high mesh counts may only get 1. In general, apply the emulsion "wet on wet", rotating the screen between each coat. IMPORTANT, ALWAYS END THE LAST COAT ON THE SQUEEGEE SIDE (the inside, where the squeegee is used). So if you are coating a 110 mesh, start on the inside, apply one coat. Then rotate and apply a coat to the SHIRT side. Then rotate one more time and apply the last coat to the squeegee side. If you are coating a 200 mesh, start on the shirt side and end on the squeegee side. If you ever need to add more than four coats, allow the screen to DRY over night before adding the additional coats.

Coating screens take practice. Start by holding the screen straight up and down. Begin as close to the bottom as possible, hold the coater to the mesh. Slowly rock the screen in the opposite direction of the coater to about "11:00" (or 1:00, for left handers). Tilt the coater until the emulsion starts to touch the screen all the way across. Then draw the coater up steadily in one even stroke. Stop at a point as close to the top as you can. Then tilt the coater back level. Then push the coater up slightly to cleanly "cut" off the coat of emulsion before pulling it away.

Dry the screens overnight. They should be level with the squeegee side UP and so that nothing touches the emulsion.

Use an "exposure test film" to determine exposure. The step method is OK, but the film works better. If you use vellum, REMEMBER to use a piece with either test method for accuracy. Mesh count, mesh color and the number of coats of emulsion all effect exposure. So you will need to test all combinations.
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Post by cromaclothingco »

Well, first of all I'd like to thank you guys for helping me through these problems ! The photocure pro emulsion works great and the detail is amazing, but the main solution was when i cut out a large black piece of thick construction paper (the first time i heard this was on here, unless i missed it in vids/tutorials)
and it works great. Three coats, one bottom, two top -- works great and the design comes completely out within 10 seconds of minimal pressure

one more question

When I wash out my screens it is only for a really short period of time, quick rinse on front quick rinse on back, then minimal pressure for 10 seconds on front and then I am afraid to wash it anymore the design is out already but there is still diazo(?) dripping down. When i put newspaper down to soak up the diazo in stencil area a lot of emulsion color comes off on the newspaper but it hasn't been effecting my stencil -- am I underexposing for the emulsion to come off like that?

thanks again!

check out my first shirt (w/ good stencil)

my 2nd color was off by a hair, but its just a promo tee for now

http://cromaclothing.com/images/bamboo_tee_detail.jpg
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Post by ROADSIDE »

Washing can be tricky... the key is PATIENCE!

I usually take the screen and wet it down with little to no pressure.
Then I usually start burning the next screen (takes about 30-40 seconds)
I go back to the screen I wet and then wash it out with some pressure.

If you are still getting emulsion dripping.... you either under exposed it (slightly) or over coated it and thus wasted emulsion.

WET - EVALUATE - RINSE - DRY = WERD!
.... I can give you my opinion but I can't tell you if it's right or not.
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