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A Good Place to Start Introduction Over the years, we have come to rely on several standard masking materials that suit our needs exceptionally well. When I say that they suit our needs, you should keep in mind that our studio uses a modified sand pot that gives us a very fine control over our air and sand mixture. With this control, we are able to do a great deal of fine detailed work. Also as I discussed in tutorial 3A, we generally use 100 grit silica carbide as our general purpose medium. This carbide is very sharp and cuts very fast which means we can use lower pressures and more delicate masking materials. The more delicate the masking materials, the easier it is to cut patterns and designs in, making intricate artwork possible. As a general rule of thumb, our studio relies on about four differing types of masking materials. They all have their advantages, and specialized strengths. So let's delve into some masking materials to get an idea of what we find is best for our shop. Contact Paper The masking material we use the most around our studio has traditionally been your plain everyday run of the mill contact paper. It's tacky, it's cheap, it comes in brilliant colors and patterns, and it is effective! We tend to stick with two colors, white and transparent. Well transparent isn't really a color, but you know what I'm getting at. So why contact paper? Well, it's sticky, easy to manipulate, and it's comparatively cheap. Contact paper is sticky enough where we can carve deep along the edge of a cut with confidence that the contact paper will not lift and expose the glass to overblast. In order to get the maximum adhesion out of contact paper, we find that we have to use a wood block and rub the contact paper down onto the glass. This gets most of the air bubbles out, and wherever there is to be a cut, we go back and give a little more attention to that area. The reason we give more attention to the areas that are to be cut is because those areas will have an edge where the sand and air are trying to get under the tape. We want to make sure the tape doesn't give in to this pressure. If it does, we'd get overblast which is a bad thing. Another nice thing about contact paper is that it can be manipulated to protect just about any shape. Granted the spherical shapes may take some additional work since the material is not that elastic, but with enough practice you can get it to work. Of course cost and availability are factors in our choice of contact paper too! Contact paper is our commonplace fixall solution. We consider it to be kind of like duct tape. It can be found almost anywhere, and can be used for just about anything. The fact that it can be found almost anywhere is a valuable asset all in itself. In a rush job and run out of contact paper? Shoot on down to Longs and get a roll of scottish plaid. It's untraditional, but it works. Well we've talked about the wonders of contact paper, but have I told you about the one thing that makes it a bugger? Let me tell you now before you go and give yourself a headache. Contact paper is designed with a rather gunky kind of glue. It's not so bad when you apply the tape, use it on glass, then remove it all in the same day or two. But when you leave it on for a few days before you take it off, it tends to equalize where it wants to reside. So when you go to remove the tape, some of the glue decides it would rather adhere to the glass instead of where it came from. What this means is that if you are cutting intricate designs into the contact paper, and don't pull them right away, after a while, some of the glue will remain on the glass. This can cause real problems. The glue acts as a resist and when you blast the glass, the glue particles protect the areas you are trying to blast leaving little clear specs where there should be frost. So to avoid this, you have to clean the glass where the tape used to be before blasting it. Try doing that on a panel where you have to pull over a thousand pieces one at a time while you are in the blast cabinet (see note 1)! No thank you! In general, the longer the contact paper has been stuck to the glass, the more glue tends to stick to the glass, making cleanup necessary before any blasting can occur. Some projects require the tape to be on the glass for up to a month as that is how long it takes to plan, cut, blast and so on! To avoid this cleanup process, we have had to go with a better product for longer term projects. Of course, the better product will almost always cost more. But in light of the time it takes to clean off glue from a pulled piece, the extra cost is well worth it. Hartco to the rescue When it comes to the long term project where the masking tape has to remain on the glass for a long time, we have found a product that does not gunk up like contact paper. It is a heavier duty, and more malleable type masking material. This material can be likened to buttercut, but it is not as thick or cumbersome. This material cuts clean like contact paper, sticks like contact paper, but doesn't require any cleanup. So who is the curator of this fascinating new material? It's a company called Hartco Inc. They don't have a website that I could find, but there are some distributors who carry the product online such as http://www.beacongraphics.com/sandblst.html. 3M Masking Tape Every sand carving artist should have a case of every size imaginable of the 3M Masking Tape. The common sizes we find ourselves using are the 1/8", 1/4", 3/8" and 1/2" tape. We always use this tape to mask the edges of our glass, especially on beveled and flat polished glass. But masking edges isn't the only use. We have found that on large stripe jobs where we may have 4 foot by 8 foot panels of glass that need 1/4" stripes, we can use 1/4" masking tape and a few guide marks to ensure the tape doesn't curve too much. This method takes a fraction of the time as cutting the stripes out of the contact paper, and can be done straight enough to get nearly the same results. Because the tape is already cut to dimension, you are also assured the stripe width is consistent, more so than if you had to cut the stripes by hand. Photo Resists Using masking tape, contact paper and specialized masks such as the Hartco product are all fine and dandy when you have a design you don't mind cutting out. But every now and again you get this commission for a job that doesn't require any layering effects, and has a lot of text. Not too long ago we were commissioned by the San Francisco Chronicle to carve several panels with full paper headlines of some their top stories from the past. Literally thousands of lines of text in their original typeface were to be blasted. No human with a brain would take on the task of cutting out every letter for such a job. This is where photoresists come into play. There are two major brands of photoresists on the market today. Photobrasive and Rayzist (in alphabetical order). Both products use a photo process to set exposed areas of film and leave unexposed areas in it's gel state so it can be washed off. The difference between the two is that Rayzist uses a transparent carrier backing that allows you to position your sandblast stencils on your glass. Photobrasives will apply the adhesive directly to the glass, then set the mask onto the glued surface. Both methods have their own advantages, so which product you decide to use will have to be a personal experience type of judgement call. Shortly after the next article on application techniques for the Contact paper, 3M Masking Tape and Hartco products, we will investigate the process of using photoresists. This oughta be interesting! And yes, there will be pictures.... Conclusion So what have we learned so far? Well, there are basically 4 masking materials we live by. Masking tape, contact paper, Hartco Inc.'s masking material, and photoresist materials. Each of these masks has it's own specialized application in our studios, and they work in conjunction with our choice in grit. So stay tuned as I finish up the next several short tutorials in the series, each one focusing on one of the aforementioned products.
See you in Glass Rumors! |
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