•The secret to cool bodies and glazes is a lot of testing.
•The secret to know what to test is material and chemistry knowledge.
•The secret to learning from testing is documentation.
•The place to test, do the chemistry and document is an account at https://insight-live.com
•The place to get the knowledge is https://digitalfire.com
Silk screen printing
Screen printing is a popular technique used to reproduce single or multi-color designs for ceramics and pottery. It has long been used in the sign painting and garment industries. In the process, a frame having a tightly stretched silk fabric holds an inking blocking stencil and a squeegee is used to push the ink through the screen onto the surface below. Great detail and crisp edges are possible using this technique. It was popular for many years among slip casters but more recently potters have adopted it also. Many art schools also teach it. Of course, it is possible to screen directly on to tiles and flat surfaces. However be aware that this is only practical if they are truly flat (like a commercial dust-pressed bisque tile). On irregular surfaces you must print reverse-reading onto a transfer (e.g. tissue paper) or right-reading onto decal paper and then transfer that to the ware. Tissue paper transfers can be done on leather hard, dry or bisque ware; decals are transferred after glaze firing and then burned on in another firing. Although many books are available on the process, more and more people search videos on youtube to learn it. Supplies and equipment can be found on ebay.com or various online distributors specializing in the process.
The most important detail to consider is how you will make your screens and prepare your negatives. To start it is best to buy a 20x24in alumina framed screen and a couple of clamp-hinges to secure it to a backboard. Then prepare your artwork to fill about 14x18in of that (most people will put many smaller designs inside this area and print them selectively onto transfer paper as needed). Take your artwork to a silk screen printing company in your city (there are countless t-shirt and uniform printing businesses everywhere) and have them expose and prepare your screen for you (they may very well charge you as little as $20 to do this). These companies have busy times during the year, depending on when you will need to be patient, give them a few weeks to finish it and bring them a few pieces of pottery as a gift, especially for the worker who actually made the screen (this will help grease the wheels the next time you come!). Then get a squeegee (the right size to print the individual designs on the screen, not a huge one) and you are ready to go.
If you wish to have complete control of the process you will need to buy equipment. The main expense will be an exposure unit (a light box in which you expose the light sensitive emulsion under the negative you have made), it can cost $500-1000. You will also need a darkroom in which to prepare screens for exposing and various chemicals and other supplies. If you wish to print multi-color consider buying a multi-color press. These devices enable you to have four screens (rotating about a center), for example, and accurately position each over the artwork to print its color. Photo realistic results can be obtained using the standard CMYK color set. These units do take quite a bit of space, but used ones are often available on ebay.com for surprisingly low prices (a few hundred dollars for example).
No matter which way to choose, you will still need to make the negative used to burn the screen. Vector illustration software to produce a PDF file is the best option to produce crisp edges and high quality (e.g. Adobe Illustrator or iDraw on the iPad/Mac). But if you must you can draw by hand, scan and use a bit image editor (like Photoshop). If you want to print your own negatives (using a laser or inkjet printer) you will need to buy clear acetate having an emulsion coating which holds the ink. These emulsion-coated acetates are not crystal clear, but the exposure unit has very bright light so they still work. Different types of these are available, watch a few videos and read about them to find the one best for your printer or type of printer. If you print yourself there the blacks will almost certainly not be black and opaque enough. Many people deal with this by simply printing twice (especially on laser printers). But a better option is to buy RIP software to control your printer directly to spray more ink and produce a blacker image. If you want to do this beware that certain brands of printer will work much better or will be better supported by the software.
It is common to use commercial underglazes for the ink, most are of course intended for painting on but some brands do have a consistency that is acceptable for screen printing. However, since ink consistency is so important for the best results, many people make their own by mixing silk-screen mediums with a stain/melt mix (if you make your own ink please check the "Ceramic Ink" link below for more information).
There is no substitute for watching and listening to someone experienced in the process explain how they do it. If you can learn little details of the process that relate specifically to ceramics (that are not covered in books and videos) you will save yourself a lot of time and expense. Then you make make the process your own and improvise from there.
If you are planning on printing decals for a production process there is a serious glaze issue you must consider (see the glossary entry for Decals).
Silk screen medium. Blend the permanent and washable as appropriate to get as much hardness as possible but not so much that it is difficult to clean up the screen. Mix that with the ceramic stain:melter mix (often stain and frit).
A professionally made screen. It uses an aluminum frame and was made in a t-shirt printing shop from a negative created in Adobe Illustrator.
Silk screening using a professionally made screen
Silk screening is a popular decorating method. It is difficult to get a better quality screen than having an aluminum framed one made at a shop that specializes in this process (you can buy those hinges from a screen supplier). This screen is 16x20 inches and I have multiple designs on it (I made them in Adobe Illustrator). I am about to screen lettering and a logo onto a tile using an ink I made (because I have found drastically different melt behaviors in commercial underglazes). I find that simply mixing the ink with water to a very thick consistency works best (it is very easy to plug up the screen if you employ hardening mediums, they are difficult to wash out).
4 good reasons to consider making your own underglazes
Commercial underglaze colors fired at cone 8 in a flow tester (this is another good example of how valuable flow testers are). Underglazes need to melt enough to bond with the underlying body, but not so much that edges of designs bleed excessively into the overlying glaze. A regular glaze would melt enough to run well down the runway on this tester, but an underglaze should flow much less. The green one here is clearly not sufficiently developed. The black is too melted (and contains volatiles that are gasing). The pink is much further along than the blue. And cone 5, these samples all melt significantly less. Clearly, underglazes need to be targeted to melt at specific temperatures and each color needs specific formulation attention. Silk screening and inkjet printing are increasingly popular and these processes need ink that will fuse to the surface of the body.
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By Tony Hansen