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Screen printing TPI Question

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Buttercup
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Screen printing TPI Question

Postby Buttercup » Wed Dec 05, 2012 4:22 am

After an exhaustive search of the archives and some Googling I cannot find a chart or other information about choosing the TPI for a specific application, onto glass. I know BE's tutorial recommends a 230 TPI for fine detail but will that also work for laying down a smooth even layer of enamel onto clear glass, please?

It's summer here and all windows and doors are open so I don't want to sift, nor do I want to airbrush as it will just become airborne. I'd dearly love to just buy several sheets of St Just but that's out of the question. I've considered matting as the individual pieces I need are quite small but don't think I can lay down a uniform, thick enough mat without tediously building up layers and firing in between.

Is there a chart somewhere which describes which TPI screens to use for different glass processes, please?

Thank you, Jen
Last edited by Buttercup on Tue Dec 18, 2012 3:39 am, edited 2 times in total.

Bert Weiss
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Re: Screen printing TPI Question

Postby Bert Weiss » Wed Dec 05, 2012 12:17 pm

Jen, Inquire with the manufacturer of your enamels. Typically onglaze style colors are much more finely ground than Bullseye frits. The manufacturer will be able to tell you what they use in their test procedures.
Bert

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Buttercup
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Re: Screen printing TPI Question

Postby Buttercup » Thu Dec 06, 2012 4:29 am

Thanks, Bert. I'm awaiting a response from the local supplier. I'll start there. Jen

tbach
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Re: Screen printing TPI Question

Postby tbach » Fri Dec 07, 2012 3:11 am

I've had good luck screenprinting on glass with glass enamels on a 110 screen - most of the work I do doesn't require a more detailed screen. I use Fuse Master enamels - both low fire and high fire, depending on project, prepared with Fuse Master screenprinting medium. I believe that Bullseye is now using Reuche enamels (Greeley, Colorado) - also lead free like Fuse Master. The online tutorial at Bullseye covers the process well. I took the class last year, but I don't follow it completely - developed my own "rhythm."

Using a 110 screen and fuse master enamels allows me to lay down a smooth layer on clear glass, or other glass . . . for instance opal or transparent. It is only necessary that the surface is fairly flat.

There is also a tutorial on DVD produced by Tony Glander - very well done, covering manipulation of images, preparation of screen, exposure and firing. I have always looked at it as my "Bible" for screenprinted images on glass. Tony is very approachable - got a lot of feedback and help from him through email.

As an alternative to screenprinting, you might take a look at Printingmaking Techniques on Glass by Jody Danner Walker - one of the methods she writes about uses transparent contact paper as a resist and glass enamel applied with a sponge dabber. This works well, too, but the coverage is not as even as it is with screenprinting. Please do not follow her suggestions on screenprinting - although I'm sure they work for her, there are better ways to create a screen.

When my wife gave me a Yudu screenprinting system (can be purchased for around $100-$150 in the US) a couple of years ago for Father's day, I had just started doing fused glasswork. For some reason, my mind immediately connected the two . . . and I have been working ever since then to perfect my screenprinting on glass skills. I like the Yudu because it has a fairly small footprint, and was designed to be used for exposure and printing. I gave up on using it for drying the screen after washing out emulsion . . . takes several days, and I just can't wait that long. I setup my drying cabinet by attaching a hair dryer to a black storage container - made a simple framework in the interior to allow me to dry 3 or 4 screens horizontally. The screens that come with the Yudu are kind of flimsy, but one of the major screen makers has started to make "aftermarket Yudu screens" that are much more substantial. At the beginning, I didn't look forward to putting the emulsion on the screen, exposing, printing and then reclaiming the screen - it seemed daunting, but by now it has become no big deal - think nothing of creating a screen for a "one-off."

If you wish, you can see some of my work at tedbachglass.com

Still a work in progress, but isn't everything?

Good luck to you. Feel free to contact me for information if you want to.

Ted

Buttercup
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Re: Screen printing TPI Question

Postby Buttercup » Fri Dec 07, 2012 4:36 am

Ted, thank you so much for your detailed response and offer to answer questions. I've seen your glass before and was impressed with your technique. I've screen-printed on both fabric and paper sometime last century and am comfortable with getting the image on the screen and ready to print. I haven't a clue what sized mesh I used then. I did watch the BE video and noted their recommendation for fine detail is a 230TPI screen. Other respondents in PM's have said much as you have done, that good results can be achieved with a coarser mesh. I plan on getting a fine mesh for line work anyway as sometimes I like to do very precise, detailed drawings. I have an unused 77TPI screen which I was considering swapping for the fine one but maybe I'll keep it and use it for 'field colouring'. I was thinking I could screen a smooth layer on, fire then sandblast a design then firepolish to clear the etched parts. I also am beginning to think I won't like that because it's not real flashed glass.

I have Kevin Petrie's book but find it a bit outside my real world unless one has access to a university art department and its equipment. I do have access to what is possibly one of the world's best UV supplies and prefer the low-tech approach of sun-exposure. I also have a photocopier, b & w printer and computer if I need to manipulate my artwork. I'd also like to use products available 'at the corner store' without having to order from overseas which leads me to my next question.

I'd like to know if I can use GMC goop with enamels for screenprinting. I have some hand-painted sample strips of enamels with CMC and others with Liquin which will be fired when I have a few more done. So far they seem to be firmly attached to the glass. I didn't use any gum arabic.

I did hear back from the local supplier where I got the enamels I am testing but she didn't have any information about screenprinting.

I haven't seen Tony Glander's video but have read good reports before and will consider getting it once I get past the set up and have done a few pieces.

So with all the good information I've been given concerning screen mesh and processing I'd appreciate knowing if CMC will work for screen printing? I have it, it's non-toxic and inexpensive and available to replace as used. If it can be used does it need any other component besides the CMC and the enamel?

Thanks so much to everyone who responded here and in PM's. Jen

tbach
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Re: Screen printing TPI Question

Postby tbach » Fri Dec 07, 2012 1:14 pm

When I first read your reply, my thought was that I hadn't used CMC . . . but after a few moments a memory bubbled up. A few months ago I ran across a technique for making paint for glass using mica, glass flux (I think this is just very finely powdered clear frit?), CMC and a little medium. The original recipe was related to producing mica dots that would not blow away after firing on glass. It worked very well . . . so I had to try it with a screen. Great results. So I think it would work for you with glass enamels. The reason for mica dot recipe having glass flux in it is to give mica some glass to attach to while firing - that won't be a problem with glass enamel, so I think your idea would work. Let me know what you find out, and I'll let you know what happens when I try it . . . now I just HAVE to.

Regards from cold and wet Oregon.

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Re: Screen printing TPI Question

Postby Bert Weiss » Fri Dec 07, 2012 2:03 pm

I'm pretty sure you have to cook CMC, I don't think it works properly if the powder is added. Once you have a concentrated cooked batch, it dissolves well in to water or water miscible medium. Klyr Fire is a 3% solution of CMC.

I would avoid klyr fire for screen printing, because it is also 97% water. If you have a water miscible medium that you purchased, there is a binder included in it. I make my own water miscible medium using propylene glycol and glycerine. When I do this, I add gum arabic to the enamel powder in the way I was taught to add when painting on glass with water as the medium. Glycerine slows down the drying time, so that your ink won't dry in the screen and mess up the printing process. You can always dry the ink with heat from a kiln, if you want to print over it. Otherwise, firing wet is a non-issue. The glycol raises the boiling point as well as lowering the freezing point. The result is, during a routine glass firing, your ink will dry on the glass before it boils and messes up the application you made.

BTW, water miscible is the proper technical term for "water friendly" medium. The only reason I would actually add water to my paint mixture would be to get a runny thin watercolor wash effect. Usually I thin my paint with more medium. Water is for the clean up.
Bert



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Buttercup
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Re: Screen printing TPI Question

Postby Buttercup » Fri Dec 07, 2012 6:33 pm

Thank you Ted and Bert for the input.

I already have CMC mixed up, just the CMC and water cooked up per the ratios recommended here and in Rick's book, with nothing else added. I used it to make the test strip enamels that are waiting to be fired. I haven't purchased any commercially-prepared water miscible medium. When I paint (apart from the new test strips I'm doing) I simply use enamel or stainers mixed with gum arabic then with either water, clove oil or vinegar. I have gum arabic and can easily obtain glycerine and propylene glycol.(I thought I had the latter but it's isopropyl alcohol.)

Bert, are you saying to skip the CMC goop and make up a batch of enamels and media with the other ingredients you've listed? Are proportions important here? I'm hoping not to have to experiment too much because of the price of the enamels and stainers, even if all the other ingredients are inexpensive. Albin only refers to squeegee oil which I'm trying to avoid.

Ted, that sounds intriguing. I'm trying to ignore a collection of Thompson Carefree lustres that came with a kiln I bought. Sometimes I have the attention span of a gnat and something bright and shiny will totally distract me. One thing at a time.....look forward to hearing your results. Thanks again, and regards from warm, sunny Queensland. Jen

Kevin Midgley
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Re: Screen printing TPI Question

Postby Kevin Midgley » Fri Dec 07, 2012 8:13 pm

take some corn starch, mix that with your medium of choice and play with that glop. See how it handles. It will be similar to finely powdered enamels at least in particle size (but not much else) :lol:

Don Burt
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Re: Screen printing TPI Question

Postby Don Burt » Fri Dec 07, 2012 8:18 pm

I picture the problem as being multivariable: Screen TPI, viscosity of the paint, characteristics and angle and pressure of the squeegee, tension of the screen material, distance from the substrate of the screen before printing. Whatever you have on hand, you can make work by adjusting those parameters. Tony's videos were helpful to me, but you're going to have to experiment. You're going to waste some paint learning. You're going to clean some screens-up after failure. You're going to need lots of paper towels.

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Re: Screen printing TPI Question

Postby Barry Kaiser » Fri Dec 07, 2012 9:10 pm

I do a ton of screen printing.
CMC based mediums for screen printing, while they work, are not optimum for screening. These mediums do not hold nearly as much enamel in suspension as pine oil or A-14. Pine oil is a mess to deal with so I only use A-14 (a Thompson product). The results are far superior to CMC based products. Glycol based products have a problem because they thin too much when dried.
If I could use CMC mediums I definitely would. We would save a ton of money when creating our paints.
Our (Kaiser Glass Paints) are A-14 based and can give very saturated colors when used.
A-14 also cleans up with water which is a huge benefit over Pine Oil based products which need mineral spirits or turpentine.

Barry

Buttercup
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Re: Screen printing TPI Question

Postby Buttercup » Fri Dec 07, 2012 10:15 pm

Thanks Don and Barry.

If I could buy A14 here I would as I like instant gratification, but none of the Oz suppliers seem to carry it, hence the hunt for a suitable medium made from locally-sourced ingredients. Buying A-14 from the US will triple the price with postage, not to mention the time it will take.

I think I'll source the ingredients Bert mentioned and hope for some guidance on mixing proportions. Meanwhile I'll try variations on the themes thus far provided. Thanks again for all the input. Jen

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Re: Screen printing TPI Question

Postby Terry Gallentine » Fri Dec 14, 2012 1:47 pm

I have been doing screen printing on glass for quite some time and used many commercial mediums. The suppliers for these mediums are few and they usually require purchase of these mediums in larger quantities. If you have a professional screen printing materials supplier in your area, you should be able to find screen printing ink of an enamel type in quart quantities. I use enamel clear mixed with gel retarder to make my medium. You need to mix enough gel retarder to the enamel printing ink that it will not dry in while you are printing but not so much that it will become greasy and smear during the squeegee pull. You will have to experiment with the right mixture of medium to your dry material (powdered glass paints) but I have had success with this mix. It has dries to a good green strength and yet burns out well.

Bert Weiss
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Re: Screen printing TPI Question

Postby Bert Weiss » Fri Dec 14, 2012 2:16 pm

glycerine added to a water miscable medium will slow down drying time. You can purchase a 4 oz bottle at the Walmart pharmacy.

Water miscible medium for hand painting or screen printing is made of propylene glycol as the main ingredient, glycerine to slow drying time, and a binder to give it green strength before firing. I prefer to add powdered gum arabic (binder) to my glass powders before mixing.

the glycol and glycerine are both for sale in food grade formulas, at soap making and food additive suppliers.

There is one thing I am fuzzy about. I am not sure if you need to add a drop of dishsoap, or not. Cleanup of a store bought medium does create plenty of suds. Since glycol and glycerine are used in soap making, I am not sure if they are the source of the suds or not? The soap is used to control surface tension.
Bert



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Re: Screen printing TPI Question

Postby Barry Kaiser » Fri Dec 14, 2012 3:55 pm

Bert,
I've done tons of experimenting with glycerine and several glycols and ethers, including Propylene glycol. I wish I had a mix that worked. But I still go back to A-14 (at a great sacrifice in $$).

Could you share with us your mix ratios so we can try it out.

My mixes would not dry due to the glycerine, and the mixes I had shed liquid when screen printing.

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Re: Screen printing TPI Question

Postby Bert Weiss » Fri Dec 14, 2012 4:23 pm

Barry Kaiser wrote:Bert,
I've done tons of experimenting with glycerine and several glycols and ethers, including Propylene glycol. I wish I had a mix that worked. But I still go back to A-14 (at a great sacrifice in $$).

Could you share with us your mix ratios so we can try it out.

My mixes would not dry due to the glycerine, and the mixes I had shed liquid when screen printing.
Barry, I have always liked working with a medium that doesn't dry. This gives me plenty of working time. If I want to dry it, I put it in a 350ºF kiln. I have never had a problem putting glass in to a 350 oven, but I have had it break in my gloved hand when removing it. So, I let it cool before handling it. My rule of thumb is, if I can handle the glass with my bare hands, it is cool enough to remove from a kiln. BTW, I seldom add water to my medium. I would only add water if I wanted to get a runny thin watercolor look. To thin for spraying, I would use isopropyl. For spraying I mix up a paste, put it in a jar with the alcohol and shake.

I use something like 4 0r 5 parts propylene glycol to one part glycerine. When I make my own, I have seen no need to measure. I was taught how to gauge how much gum arabic to add to dry paint by Albin Elskus (The Art of Painting on Glass, currently in print) I add a squirt of dishsoap. I found an internet source for glycol and glycerine by the gallon that are really cheap.

The purpose of the glycerine is to slow the drying down to the point where screen clogging is not an issue. For me when painting, I can keep mixed paint on a glass palette for a month and still use it. Reconstituted dry paint does not flow from the brush like freshly mixed paint. For this reason, I tend to mix paint and use it. I don't store mixed paint for a long time,
Bert



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Re: Screen printing TPI Question

Postby Terry Gallentine » Sat Dec 15, 2012 10:15 pm

I made the assumption that you were using a photo emulsion when you were screen printing. If you are using something like a dual cure photo emulsion, using water based mediums can cause some problems unless you use an emulsion hardener to protect the stencil from breaking down. This is especially true if you add the abrasive component of ceramic powders to the mix. If on the other hand you are using handmade lacquer based stencils, I suppose that the water based mediums would work. What type of stencil or emulsion are you using?

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Re: Screen printing TPI Question

Postby Buttercup » Tue Dec 18, 2012 3:34 am

Thank you Terry, Bert and Barry for the additional information. Terry, I'm not sure if your question about the type of emulsion was directed to Bert, Barry or to me so I'll tell you what I bought to use. I haven't used it yet. It's Ulano Proclaim, and is apparently resistant to both oil and water-based 'paints'.:

Diazo-Photopolymer (Dual-Cure) Emulsions
Ulano's diazo-photopolymer emulsions represent a dynamic step forward in dual-cure technology. The Ulano LX series of dual-cure emulsions provide higher solids content, faster exposure times, superior resolution and definition capabilities, and resistance to both solvent- and water-based inks. Ulano's LX dual-cure emulsions are partially sensitized and should be handled under yellow safe light conditions before exposure.

Diazo-photopolymer ("dual-cure") emulsions resemble conventional diazo-sensitized emulsions inasmuch as they are sensitized by diazo resins and contain PVOH and usually PVA. They also contain oil-based water and solvent-resistant acrylate monomers/oligomers, and a photo initiator and accelerator. Because the acrylate increases the emulsion's solids content, it is possible to use less PVA in dual-cures. This spells easier reclaiming and less acetate staining. The high solids contribute to faster drying, sharp stencil shoulders and printing acutance, better mesh bridging, and higher build per coat for relatively lower Rz values.

I also just realized that it should be in the fridge, given that it's around 32℃ here today.

I have only found one supplier of enamels for glass for screenprinting. They are opaque and fire at 500-630℃. They sell a medium to mix them with for screen printing or hand painting. I've emailed them with some questions but haven't heard back yet. If the enamels are similar to those I already have it may make sense just to get the medium, if it's suitable.I don't know if the medium will take the higher firing that the enamels I have require, or if it will take multiple firings. I'll phone them if I don't hear by tomorrow. Thanks again, Jen
PS. Nothing on their site says they are 'vitreous enamels'. Maybe they are commercial bottle-coatings??

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Re: Screen printing TPI Question

Postby Barry Kaiser » Tue Dec 18, 2012 5:00 pm

Jen,
We have premixed vitreous enamels for screen printing (see our site for many examples) that mature starting at 730. The shipping to Oz is $16.95 for a set and I will throw in some flux to adjust the viscosity. If you are interested email me off the board.

Barry

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Re: Screen printing TPI Question

Postby Bert Weiss » Tue Dec 18, 2012 6:14 pm

Jen, 500ºC - 630ºC are vitreous enamels designed for glassware. They will mature at a temperature, beneath the temperature, at which the glasses will slump out of shape. Enamels designed for ceramic dinnerware vitrify between 750ºC and 850ºC. These are appropriate for use on glass fired in the fusing range. Often, in industry, these are classified as ceramic onglaze colors, and they don't really know that they work on glass. So, if you ask for vitreous glass colors, you get the low fire ones. Ferro, the company I have worked with, sells in Australia. I don't know the logistics of buying there, though. Barry's colors are good too.
Bert



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