by Hank Kaminsky
Commercial pattern letters are available from foundry supply houses in a variety of fonts and sizes. These sprigged or sticky-back letters can usually be applied to flat surfaces and can then be molded. For logos or calligraphic lettering or where the type styles or flatness of commercial pattern Ietters are not acceptable letters can be carved or sculpted out of wax or plastellina and then molded, cast in wax for the lost wax process or cast in pattern material such as plaster or Bondo, etc. for ramming up in sand.
Letters smaller than 3/8" are another problem. Intricate forms like these are difficult to carve out of wax or other material. Commercial pattern letters are not available in these small sizes.
The rubber stamp industry offers a quick and mostly acceptable method to produce lettering for these situations or when the time is not available to carve a logo or special design. I'll get into the part of this process which makes it less than perfect later.
Some rubber stamps are made from a UV catalyzed polymer. In this process a pool of the liquid polymer is poured out on a glass sheet within an area lined with dams made of foam strips. A sheet of negative film with the lettering on it is laid over the pool and a second sheet of glass placed on top. The sandwich is exposed to ultraviolet light. The polymer hardens under the clear areas where there is lettering and stays liquid under the opaque areas of the film. After a very precise period of exposure the sandwich is disassembled and washed. The unhardened polymer washes away leaving the lettering as raised forms. The precise exposure is necessary so that the shoulders of the letters form at an angle which will support the use pattern of the stamp.
When you bring your lettering, black on white paper, to the rubber stamp maker tell him/her to turn the negative over so that the letters of your "stamp" are right reading instead of reversed as they would be for a proper rubber stamp. Of course you only need the rubber part not the stamp holder, which will save you some money.
These stamps can be used as patterns for sand casting or can be rubber molded for casting in wax. I imagine they can be burned out in a lost wax mold but I have made no experiments in this area.
One disadvantage to this kind of lettering is the width of the shoulders and the fairly shallow angle they form as compared to good pattern letters from a foundry supply house or letters you can carve from wax. Pattern letters have very steep draft angles and make a very attractive, clean letter when cast. What you see when you look at a letter cast from a pattern is the letter not the letter surrounded by a halo of shoulder. For many applications this problem is of no importance. It's just one of those things most people wouldn't notice.
Another problem with this system over pattern letters or letters that are carved and then cast is the depth of the raised letter. I have found a rubber stamp maker who claims he can make these stamps about 3/8" thick. Pattern letters are often deeper than the 1/8" rubber stamps typical in the industry. Those deeper letters have more quality when seen on a plaque or sculptural form. However if this lower quality is acceptable this system is very handy.
In my shop I also use another method for making letters since I have the added problem of putting my lettering on the complex surfaces of my sculptures. I lay down a layer of plastellina on the surface of the casting pattern to which I want to add the lettering and then, using a potters needle tool held at the desired draft angle I will cut away the clay from the letter forms. I take silicone rubber molds of the letters and cast them in plaster (or silicone if I need a flexible letter). The aluminum egg sculpture seen in the ArtMetal features page a while back used this method to make the lettering.
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