I think that you know what a silk screen is... but let me describe it in my words so that we can get our terminology in sync.... a silk screen is a piece of mesh fabric held taut in a frame. Some of the holes in the fabric's mesh are "clogged up" to prevent ink from passing through. When the silk screen is placed against a "work piece" and ink is "squeegied" across the screen surface, ink is deposited on the work piece whereever the screen wasn't "clogged". The secret to silk screening is clogging up the mesh in the "right places" and squeezing the right amount of ink through the rest.
The first question most folks have is "Where can I get the stuff? And, how much will it cost?"
Art supply outfits seem to be the best resource. Locally, I buy from "Dick Blick" which is an Illinois/Iowa chain. Larger metropolitan areas should be easier. For clarity, I've included catalog links to Dick Blick catalog pages for key items. My purpose is to more clearly describe the items in question so that you can comparison shop for equivalent items. The links are "good" as of October, 2008. (If it turns out that the page locations are too volatile, I'll have to rethink how I do this.)
You would probably like a thumbnail of the materials and estimated costs before we go too far, so, here goes:
Other odds and ends...
The easiest to use is "air dry textile ink" to print on porous fabrics. It cleans up in water and air dries in 30 to 60 minutes. It is best to "heat set" this ink with an iron at 300 degrees to reduce its tendency to wash out of the cloth after many washings. Once dry, it does resist washing out, but not as effectively as if it is "heat set". These inks do not seem to be as dense as others, and I have not had good luck putting light colored ink (white, yellow, etc.) on very dark cloth (deep red, black, deep blue.) Dark inks (black, navy blue, red, etc) on white, pastels and medium dark colors seems to work very well. This also prints well on paper, at least for larger (e.g. 24 point) letters.
The other major ink used for textiles is called "Plastisol". It does not air dry at all. It is the most commonly used ink for multicolor screening, because it does not air dry in the silk screen, giving you time to briefly heat set the surface of each printed color before putting the next color on. The problem with plastisol is that it requires more equipment to finally "set" the ink properly. I personally don't like the texture of plastisol... it has an almost rubbery feel. But it covers very well and if you must use light colors on very dark materials, then it would be the choice. Faced with this, I'd pass the buck over to a "professional" because I don't want to put out the bux for the "heat setting / drying equipment".
On ribbons and vinyl, I use some really obnoxious stuff called NAZ-DAR/KC (GV series). Special cleaner and lots of protection and ventilation required... not a very good winter project!
On Pinewood Derby Plaques, I use an oil base printing ink. A quart of this lasts me several years at 50 plaques a year.
All of these "inks" are thicker than normal paint... reminds me of pudding... and manufactured specifically for silk screening. Inks may specify a minimum screen mesh so that the pigments can squeeze through the holes.)
So, how do you make a silk screen? There are several ways, but let me describe the way that I prefer, because it fits my limited artistic skill best!
Step 1. Prepare the pattern that you want to have printed on the workpieces. There are lots of ways to do this... I use computer generated graphics and lettering printed with an ink-jet printer on special transparencies (3M Brand CG3460). I've also use "press-on letters" on clear acetate, hand-drawn inked pictures on clear acetate, photocopies on transparencies (usually not dense enough... needs to be darkened somehow) and cardboard cut-outs. Anything that will prevent light from reaching the screen where you want ink to pass through the screen. With ink-jet printer transparencies, doubling (ganging) a pair of identical transparencies seems to work best for me. (If you do this, trim them to different margins widths so that you don't have two edges together.)
Step 2. Get a frame and mount a piece of "silk screen material" in it. You could make your own, but the commercially available frames are cheap enough. Some come with with a piece of Multi-filament silk already installed. (I prefer mono-filiment, because it is easier to "wash out" my mistakes, but it is sometimes more expensive per yard.)
Step 3. Wash the new screen with soap and water, then rinse well and allow to dry. This removes any "sizing" that might have been in the fabric.
Step 4. Apply a coat of "emulsion" to the screen, covering totally with a thin, even coat. There are tools for this if you were doing a lot of screens, but I use a spoon and the squeegie to do one or two screens. Set it aside to dry in a dark, dry place. The emulsion that I use is "photo-sensitive," but mainly to UV light. It takes about 1 hour to expose a screen with a normal 300 watt bulb separated by 17 inches, so it is not necessary to work in a "dark room". However, sunlight is much richer in UV, so avoid sunlight until the screen has been completed.
Step 5. Estimate the exposure time. The emulsion will probably come with some instructions. (Remember that exposure time is inversely proportional to lamp wattage and is proportional to the square of the distance between the lamp and the screen.)
Step 6. Lay the silk screen, face down under the lamp. Lay the transparencies and cut-outs, centered and face down, on the silk screen. carefully place the glass over all this to hold the transparencies and cut-outs in place firmly against the screen. It might be necessary to put a flat surface, like a large book under the screen to keep everyting firmly together.
Step 7. Turn on the lamp and expose the screen for the prescribed time. Time this carefully, because you may need to re-do it with more or less time, depending on how good your estimate was (step 5). First time out, you may wish to "calibrate" your exposure equipment. I did this by using a transparency with numbers printed. As each number of minutes elapsed, I would slide a sheet of cardboard along the screen to cover that number on the screen. When all the numbers are covered, stop the exposure and go through the next steps to see which time gave the best results... enough time, but not too much.
Step 8. Turn off the lamp, take all the stuff off the screen and gently wash the screen. The areas which were exposed to the light should not wash out. The areas that were masked should wash out. I like to use the spray on our kitchen sink for this... holding it so that it sprays along the plane of the screen and working alternately from both sides. Lukewarm water is best at this stage. After a minute or so of this, the masked areas should be totally free of emulsion. To check, hold the screen up toward a lamp and look thru it. Check the whole pattern! If the screen was exposed for too long, some areas may not wash out properly. In that case, you may use a gentle scrub brush to loosen the remaining emulsion.
If the time estimate was right, we're just about done... set the screen aside to dry.
If not, mop all the moisture off the screen and use the screen wash to remove any of the emulsion that is left. Set it aside to dry. Adjust your time estimate, and start over with step 4.
Step 9. We've got a good screen! After it has dried, expose it some more just to harden the emulsion for sure! Another hour under the lamp or a few minutes in the bright sun light should be sufficient.
|Hey! It looks like fun! Let's try it!|