FIGURE CONVERSIONS:
CASTING:
Basic Casting
by Alvan Fisher, Jr.
In the first article of this series we discussed the various tools and materials, including paints and adhesives. In this article we will consider casting figures in lead.
The molds discussed here are the simple gravity flow ones used by hobbyists, not those used by professionals that require centrifuging. Today, most molds are made from either metal or room temperature vulcanizing (RTV) silicone rubber. Older molds -- such as those for flats sold by A.C. Gilbert before World War II -- were made of metal, while more recent molds for rounded figures tend to be made of RTV. A few hand-made plaster molds may be around, but they are rare and normally not sold by dealers.
The first requirement for casting is to find a suitable source of metal. This is not as easy as it once was, owing to both advances in technology, and safety reasons. The linotype slugs and letters I used as a boy are hard to find, as is lead solder in bars. The latter normally come in either 50/50 or 70/30 mixtures of tin and lead. Solder provides better detail and malleability than linotype, but the 70/30 mixture can bend too easily for thin parts such as rifles and bayonets. Coil solder with a rosin core is not recommended as the rosin emits noxious fumes when heated.
Pewter and white metal alloys normally have a tin content greater than 90 percent with little or no lead. Unfortunately, they are also more expensive than lead alloys -- about eight dollars per pound from a metal dealer compared to one to two dollars for lead ingots sold in gun shops. Two sources for small quantities of tin alloy (Belmont and Conquest) are listed at the end of the article.
A ladle is required to heat and pour the metal. For years I used one that came with an A.C. Gilbert set I was given in the 1940's; the kitchen stove served as the heat source. Recently, I invested in an electric ladle for about US$35 and greatly prefer it. It is superior both for ease in handling and the ability to work outside. If you do a lot of casting, you might want to invest in a ladle with a center flow and a temperature regulator.
Whichever you use, be sure to use gloves and a mask when handling to reduce any risk of lead ingestion or burns. The softer (70/30) metal flows freely, but castings made with it require more preparation. Fortunately, excess metal (flash) is easy to remove using a file or knife. Newly-cast figures should be allowed to sit in the mold for a few minutes to prevent their crumbling when removed from the mold.
Impurities build up fairly quickly in the form of a scum on top of the molten metal and must be removed to ensure a good pour. These impurities come from two sources:
Periodic skimming the surface with an old spoon helps eliminate the scum during the casting session. Whenever the lead supply gets low, pour the remainder on an old board. Then knock the ladle on the board to knock loose the oxides.
Metal purifiers can be purchased from metal suppliers, but they an be costly. An old trick is to add a small flake of beeswax (about the size of a fingernail) to the metal prior to skimming.
A point well worth remembering: Hot castings look the same as cold castings, so be careful. Large castings, such as horses, will require fifteen or more minutes to cool to the point where they can be handled without gloves. My favorite gloves are a used pair given to me by my son -- a San Diego firefighter. With them, I can hold a new casting without the least discomfort. I also use a good face mask to avoid inhalation of any fumes and safety glasses to protect my eyes.
A mold requires lubrication to assure good separation between the mold and figure. Candle soot is used with metal molds; don't use your outdoor grill or you might end up with a pool of metal as I did! RTV molds use talcum powder or graphite powder as a lubricant.
I purchased a can of Micro Mesh graphite powder from Coastal Enterprises for about ten dollars, and now have enough to last for the rest of my natural life! The graphite gives a black sheen to the mold and does produce better castings as advertised. However, I found that the first castings made after application often had small pits that required filling with auto body filler. The powder looks similar to the graphite used to lubricate locks, which you might try if you feel like experimenting. But, talcum works nearly as well and is cheaper.
Temperature control is important - "too low" results in a poor casting while "too high" may damage the mold. Instructions that came with the Prince August molds suggested using a wooden match (such as the long ones used in starting fires in a fireplace) as an indicator. If held in the molten mixture for about 6 seconds, a wooden match stick (without head) that smokes but didn't burst into flame indicates that the metal is at the right temperature. As we don't use our fireplace, I use disposable wooden chop sticks liberated from a local Chinese restaurant.
The mold also must be at the correct temperature to obtain passable castings. I almost always have to reject the first casting because the mold cavity hadn't warmed sufficiently.
Too much heat can ruin a mold, so it is best to limit yourself to half a dozen castings at a time. You can use a second mold or clean castings while allowing the first mold to cool. Ambient weather conditions have an affect here: you can make more consecutive pourings on a cold, blustery day than you can on a hot, windless day.
New RTV molds almost always require that air channels be cut before the metal will flow freely to all parts of the cavity. The channels, which permit air to escape from the cavity of a tightly clamped mold, are cut with a razor blade or X-acto knife.
Although not always possible, it is best to cut a thin channel about 1/32nds of an inch wide, from the cavity upward to the edge of the mold. When using molds with multiple cavities, channels can be cut from the interior of one cavity to the interior of the second. Even if the channel doesn't go all the way to the edge, it will still act as a reservoir for entrapped air.
While not entirely successful, I have had some luck at improving flow to the corners of the base by sticking a needle from inside the cavity through the side of the mold. Be careful to insert the needle at right angles so that the newly poured lead doesn't lock the casting in the mold!
Metal molds don't have the flexibility of RTV molds, so that air passage must be considered during design. These molds usually fit into a fixed clamp and have provisions for rigid handles.
Conversely, one of the advantages of RTV molds is their flexibility. Use spring-loaded clamps to keep RTV molds tight, with pressed board panels between the mold and the clamp to distribute the pressure evenly. C-clamps can be used in lieu of spring clamps, but can be tricky: too much pressure prevents the molten metal from filling the cavity completely, while too little pressure allows the metal to flow out through the mold sides and bottom. Purchase of additional clamps and pressed board panels permit using several molds simultaneously, thus providing more cooling time between pours.
I use a large pair of wire cutters to cut off the sprue and heavy flash. A rasp is used for initial cleaning of the casting, followed by progressively smaller files and emery paper. I use gloves and a mask during all stages of trimming to keep from ingesting the lead.
If you do the final trimming in the family room while watching TV as I do, use a catch cloth to protect rug and upholstery to preserve marital harmony!
Make holes for the head, arms, and pack as required using appropriately sized metal cutting bits purchased at a local auto supply or hobby store. A drill press makes it easier to put the holes where desired -- I use the type that holds my power drill with acceptable results.
If you are not going to add additional details, you are now ready to assemble the figure. I use a gap-filling super glue (Zap-a- Gap+), which works well. Be careful not attach your fingers to the casting -- I left a couple of layers of skin on a Prussian Guard last night! In severe cases, surgical removal of the object from your fingers may be required. Use a small amount to tack the two pieces together initially. When satisfied with the pose, apply a second coating to the joint to bond the parts together permanently. Fill any remaining gaps with auto body filler. A little final smoothing with emery paper and you are ready to start painting.
Most of the materials described in this article can be purchased from toy soldiers dealers. Three I've dealt with are listed below. Other sources can be found in the classified pages of your phone book, in directories of manufacturers found in your local library, and in hobby magazines.
In this article we examined some of the basic methods used to cast toy soldiers. This process is not hard and the pleasures derived will more than compensate for the few dollars spent on materials. The next article will discuss some of the basics for making room temperature vulcanizing (RTV) silicone rubber molds from your own master patterns.
| Last Updates | |
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| 27 January 1997 | page first published |
| Article by Alvan Fisher, Jr. Material originally distributed to the Internet by Larry Jeselon (ljeselon@ccinet.ab.ca) | |
| Comments or corrections? | |