# cleaning burnt emulsion?



## woodja (Feb 12, 2009)

anyone know any way to clean emulsion that has sat for a little while? we are starting a business here, and i had my partner clean the screens the other night. he let the emulsion cleaner dry on one, and now the emulsion won't come out. any ideas? i don't want to have to scrap this. i have most chemicals available here, and a power washer. but nothing seems to work.


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## mrvixx (Jan 13, 2009)

Locked emulsions is very hard to come out. try laquer thinner or bleach.


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## woodja (Feb 12, 2009)

threw some paint thinner at it a few minutes ago, i think i heard the emulsion laughing at me. i'll try the bleach next. otherwise, that's $20 out the door. oh well, guess it takes some burnt $$ to start a business.


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## Tj Ryonet Tech (Jul 28, 2008)

Take it to a car wash and try and muscle it out with a high power pressure washer.


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## Bill Hood (Apr 11, 2007)

Do not use "high pressure" on a screen. Too much pressure will destroy the tension and prevent you from achieving satisfactory results in the future from this screen.

Do not use "lacquer thinner" on dual cure polymer emulsion as it will lock the emulsion into the mesh and it will never come out.

Do not underexpose the emulsion, as this will "lock" the emulsion into the polyester and prevent it from being reclaimed.

If the emulsion was exposed properly, you can easily reclaim it with ordinary emulsion remover (Sodium Metaperiodate) or sometimes with ordinary bleach.


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## woodja (Feb 12, 2009)

guess that means it was my fault rather than his  could have been because i underexposed it. i dont remember setting the timer on that one. 

i tried the pressure washer i have out back (2600 psi i think) and im pretty sure i cleaned the lawn more than the screen.


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## drunkswithapress (Jan 15, 2009)

hey player, i use bleach to reclaim my screens, check your local wal-mart or dollar store for good prices. I also have some screens that i have bought used and thier emulsion is locked and bleach will not get it out. I've heard of an aerosol product called "sprayaway" that people swear buy, i haven't tried it. I'm ghetto though, meaning i burn my screens in my basement,wash/reclaim them in my bathtub, and print in one of my daughters rooms. I HAVE been told not to use laquer thinner. I use mineral spirits to clean the ink. I use plastisol ink. I've never heard of under-exposing being a problem... if it's under-exposed, your stencil washes out right??? good luck.


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## woodja (Feb 12, 2009)

the bleach idea almost cleaned one of the screens. still a little emulsion left, but hey, its better than covering the whole thing. 


cleaning process:


card off excess ink
mineral spirits to clean off ink
spray with pressure washer
hit with emulsion remover
scrub/pressure wash
Renu-It Ghost remover
this seems to work on the screens that were burnt correctly. i'm wondering though if the heat from the 500w halogen is burning the emulsion. it's over 2 ft away. oh well, i guess i'll just have to learn as i go here


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## drunkswithapress (Jan 15, 2009)

I usually leave the bleach on there for a few minutes to soak and i also use a soft bristle brush to scrub the screen. and spraying hotwater to rinse it works well. i just repeat until the screen is clear. i also use a 500w halogen, and i haven't had any problems.


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## mrvixx (Jan 13, 2009)

I mentioned bleach but it is not the correct product to use. you should try and degrease right after you remove the ink.


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## softhandprinter (Feb 13, 2009)

You're probably gonna waste more than $20 in bleach and time trying to reclaim that screen and it won't be very good when you're done - besides bleach is poisonous and you don't want to be breathing in chlorine vapor or having it splash in your face. Bottom line: DON'T let emulsion remover dry on a screen before you reclaim it!


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## greattatee (Dec 5, 2008)

get a lil bottle of "*easy strip*". mix 1 part *easy strip* and 3 part water, works great! if it really a pain. spray easy strip right on out of the bottle and watch it run off the screen before you get done spraying it down


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## JeridHill (Feb 8, 2006)

I want to reiterate what a couple of people have said since I think the point is being lost in this thread of "how to's".

When you apply an emulsion reclaimer on the screen and let it dry, you are locking in the emulsion by a chemical bond. It is extremely difficult to get out. I have been successful with a 3000 psi pressure washer, but as it was said before, the more pressure you apply to a screen, you lose the screen's tightness and quality of print. Here is a Q&A from Ulano regarding the screen reclaiming process:

Q1:Why isn't my stencil remover working?
It is very important to never let the stencil remover dry. It locks the stencil in the mesh with a permanent chemical bond.

Under exposed stencils are harder to remove than completely cured/exposed stencils.

Under exposed means some of the sensitizer did not cross link. This is always on the inside of the stencil because invisible UV energy didn't have enough time to move all the way through the stencil to the inside. Penetration of UV energy is not 'linear'. The deeper the UV energy has to penetrate, the longer it takes based on the physics rule called the Inverse Square Law. If you double a distance energy has to travel, it takes 4 times the energy - NOT double. Many low energy UV lamps may never penetrate a thick stencil.

When you spray stencil remover on the stencil, it has to penetrate and attack the chemical crosslinks formed by UV exposure. No crosslinks - no easy stencil removal.

The stencil remover chemical creates another reaction with under-exposed stencil and forms a chemical bond with the mesh that is very difficult to remove.

Q2: How should I use stencil remover?
To remove a stencil from the mesh. A chemical is applied to a stencil that breaks apart the basic chemicals that were mixed together and cross linked when they were exposed with Ultra Violet light. The proper de-coating chemical works like a key in a lock and the stencil falls off the mesh and washes down the drain.

Q3: ?
Penetration
Fully, or even over exposed screens, actually reclaim easier than under exposed screens.
Screen makers under-exposure to keep fine lines fro closing up and choking the actual ink print. Under exposure does reduce that problem, but at the cost of stencil durability and the ability to reclaim the stencil. 

Many reclaiming problems result from mistakes made earlier, during the stencil-making process. Chief among these is underexposing the emulsion. Underexposed emulsion can be virtually locked to the threads of the mesh and may resist all efforts to reclaim it. The solution is to buy and learn how to use an exposure calculator or 21 Step Gray scale to measure stencil hardness. 

My stencil doesn't want to reclaim
Q4: Can I used bleach to reclaim my mesh?

Bleach
I've discussed your question about using bleach as stencil remover with our senior chemist. He says that bleach is both slower than SMP and environmentally harsher. 

Controlling the dilution of bleach as it contacts the stencil during decoating is difficult. If the concentration is too high, there's danger of a lock-in from an oxidation-reduction reaction; too low a concentration, and there's no effect. 

The optimal concentration varies for each emulsion blend. Certain types of emulsion, such as 925WR, are hard to reclaim with bleach of any concentration.

So there it is: bleach is slower, less green and, most importantly, considerably less reliable than SMP.

The most common reclaim chemical in the screen industry is sodium metaperiodate. This is a salt that is related to household chlorine bleach, but without the harmfull characteristics associated with bleach. 

Typical emulsion removers contain sodium metaperiodate or salts of periodic acid.

Problems during decoating or reclaiming of the screen occur when the screen was underexposed or if the emulsion is extremely water resistant. Solvents may cause underexposed emulsion to harden and "lock in", resulting in difficult reclaiming and excessive emulsion haze. The higher the water resistance often emulsion the more difficult it is to reclaim. Emulsion that is only solvent resistant should reclaim easy. Never let the reclaimer dry on the screen. 

Why am I having trouble reclaiming? The old emulsion won’t come off the screen. Many things can cause reclaiming trouble. The most common cause, however, is underexposure of the stencil and/or under cured emulsion. If the emulsion is not completely dry before exposure, the soft, wet emulsion remains inside the dried outside surface like a sandwich. This uncured emulsion will react with inks, solvents and other chemicals during the printing process and chemically lock onto the screen. This will make it very hard to reclaim the screen later. Other factors that promote easy reclaiming are proper exposure and cleaning the ink completely and then removing the ink wash with degreaser. Lead with - The basics of cross linking

Reclaiming The reclaiming problems are one of the biggest culprits of improperly exposed screens. If a screen is underexposed the subsequent stencil will have good detail but will be soft or slimy. This soft stencil will not reclaim as easily because any solvents in the ink mix with the soft emulsion and stain the mesh. If a screen should need to be underexposed for some reason always be sure to post expose the screen after it is washed out and dried. While this can be accomplished by placing the screen back on the exposure unit and exposing without the film positive, it is often just as easy to place the screen in the direct sun-light for a few minutes. Locked by chemical which is NOT breakable

Difficult reclaiming if Under exposed
Mixing stronger is not necessairly better. 
Only a minor amount of the Sodium Metaperiodate in reclaimers is needed to breakdown the stencil. The large amount of water is what allows the chemicals in reclaimer to penetrate the emulsion coating so they can do their job.

Stencil remover has little effect on 'underexposed' stencils. The sodium metaperiodate in stencil remover attacks the cross links that hold the stencil in the mesh. If you underexposed, there aren't lots of links to break, and you have to use brute force to punch the stencil from the mesh, instead of the smooth breakdown of the stencil like turning a key in a lock.

So fully harden your stencil, mix reclaimer properly and apply as directed, and absolutely use the power washer to blast it off after the reclaimer breaks it down.

The longer a stencil remains in a screen the harder the emulsion is likely to become. Get in the habit of reclaiming your screens as soon as you are finished with them. Emulsions can also become excessively hardened through contact with certain strong solvents. If your exposures are bang on and you’re still running into reclaiming problems, try switching to a different wash-up or screen-opener. 

Sometimes stubborn bits of stencil hang on despite your best efforts. Try reapplying the stencil remover or dehazer to that spot. Wait a few minutes and hit it with your pressure washer. Adjust the nozzle to deliver a more finely focused spray. Remember that as the water jet becomes narrower its power increases. Don’t let it stay aimed at one small area. Keep it moving. 

Although, we've talked mostly about direct emulsions, the reclaiming process for films is similar. In fact, films can be easier to reclaim. Just remember that indirect films are gelatin-based and require the use of special stencil removers.


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## RichardGreaves (Nov 7, 2006)

Water resistance of a stencil depends on the complete cross-linking of the ingredients. If the exposure time is too short, or doesn't move all the way through the stencil, the cross-linking is incomplete and complete water resistance isn't achieved.

UV energy reacts with diazo or photopolymer sensitizer in the stencil and causes a chemical cross-link between the two components that make up the "emulsion". Linked together, and woven in and out of you mesh, the exposed stencil will not dissolve with water and rinse own the drain.

Sodium MetaPeriodate (SMP), attacks these cross-links, releasing the stencil so it will dissolve, and you can wash it down the drain.

If you let this "soup' of stencil remover & emulsion dry, they form a new chemical bond that is permanent. There is no chemical to break down this chemical combination except the brute force of water pressure. Yes you will also lose mesh tension blasting the mesh if it vibrates like a drum, if the stencil doesn't come out.

This effect also happens with under-exposed stencils.

The stencil worked OK with harmless plastisol, but if you clean the ink with a strong solvent, the solvent will attack the defenseless under-exposed stencil and chemically bond it to the mesh. 

It is harder to reclaim under-exposed stencil because stencil remover attacks sensitizer cross-links.

???
If lacquer thinner broke down stencils, how could people print with lacquer ink? Waste of time.

Jerid Hill already explained that bleach is inferior to SMP. Many will answer, "but it works". When you go home I want you to use the key to open your door, not the kick of brute force. It takes more bleach to do the work of a small amount of SMP.

http://www.t-shirtforums.com/screen-printing/t60134.html#post358845


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## Bill Hood (Apr 11, 2007)

See this post for more information on the subject...

http://www.t-shirtforums.com/p821210-post40.html


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