Following a Master Model Maker - HMS Lion
By George Elder and Bruce Gordon
Part 12
Questions & Answers About Model Making
From Tom Stockton:
(1) When the "master" model is finished -- it is used to make a mold (or molds) to cast models?

A:  Yes. The hull and each of its subcomponents are used to make molds -- with parts such as the Boats, cranes, etc., being done in molds that can hold several parts at once. The Germans have a technique that allows them to cast nearly an entire model in situ, but that involves a level of mold making that is beyond my knowledge.

(2) Roughly, how many molds can be cast from a single "master"?

A:  It depends on the complexity and material being used. For example, pewter melts at a relatively high temperature, and this can degrade molds much more quickly than will an alloy with a lower melting point. Moreover, if a certain part is very thick, such as the hull of an ocean liner, the volume of metal will cool more slowly, and thus expose the mold to heat for a prolonged time -- with a correlating negative effect on the mold. In resin casting, removing the pieces from the molds is the main concern. The high vacuums used in some resin casting techniques can intermix with undercuts and the like, and form trap-like areas that pull on certain aspects of the molds. This can result in tears -- or so I am told. A way around this it to use complex multipiece molds, which fit together sort of like a puzzle. These can be expensive to make. I have no idea how the German mold-making process works, and I suspect that is a process that will remain kept close to the vest. In general, the mold of a small ship like a destroyer will last longer than one for a large complex ship. One may get 200+ good copies from the mold of a DD, and less than 100 for a complicated battleship. Lastly, the type of material used to make the molds is very important, and will also influence mold-life. These are just generalities!

(2) Roughly, how many molds can be cast from a single "master"?

I answered this incorrectly because I was in too much of a hurry. Usually, a model maker uses the initial master to first make submasters. These submasters are then used to make molds, and are often damaged during the mold-making process. However, this does no harm to the master. Thus making new masters for molds is not such a daunting proposition... unless one makes so many submasters that the original is dinged beyond repair. Well, this is my understanding.

(3) And then, how many models (or sets of parts) can be expected to be cast from a single mold?

A: This is totally dependent on how the mold is arranged and has no single answer. In general, parts with smooth surfaces are less stressful on molds than would be a complicated AA gun with shields and lots of barrels.

(4) I know it has been discussed here on the message board before -- metal vs. resin -- but from a model maker and/or retailer's standpoint, is there a big advantage to casting in one medium over the other?  If I recall correctly, many collectors prefer the "heft" of metal models, but resin is "easier" on the molds... and also a little easier to pick up the finely modeled details. Or am I not remembering correctly?

A:  Resin is not always easier on the molds!  Furthermore, a bad resin casting results in a complete loss because the resin cannot be reused -- while metal can. There is great debate in this area, and all sides have valid points. The casters who prefer resin opine that it offers excellent resolution and crispness (sharp angles) that is hard to match with other materials. Extreme heat is not required, and some find this an advantage. Those who prefer metal note that guns and masts can be bent back into shape should they be tweaked, although the newer kinds of resins have considerable play. Metal may be easier to strip and repaint than resin, while the newer resins are less prone to pitting. There are numerous issues here, and I'm not getting into all them.

Overall, I think the metal casters have a wealth of experience to draw upon that goes back over 100 years!  The artists in this area understand different alloys and how to use them and their work speaks for itself.  Resin is a more recent tool, but Alain, Len Jordan, and others have amply demonstrated that great detail can be captured. Moreover, the newer resins are very stable, which is something most metal alloys have always had -- other than the dreaded lead-rot disease. I have no preference here, because both materials offer good results. I know that the Lion will be made of a resin material that takes quite a while to cure -- and this will slow production. The wait is worth it because of the material properties of the resin, which is said to be capable of capturing great detail while also offering a good degree of flexibility and long-term material stability. There are well over 4,000 types of resin, so many choices exist. As for metal alloys, there is much room for experimentation here, and Herr Kraus, Norbert, and others are constantly seeking to refine the materials they use.

From Chuck Duggie:
(5)  I have some small experience in metal and resin casting, D&D figures and micro-armor. I presume you make the masters a certain amount oversize?  Thereby allowing for shrinkage in molds and castings, so that the finished ships come out at 1/1250. If I recall correctly, we allowed 4% shrinkage in our particular alloy so made our D&D figures 4% oversize.

A:  The amount of shrinkage factored in depends on the type of resin or metal alloy being used to make the castings. Some resins, albeit they are a bit more expensive, have no appreciable shrinkage. This is the material we have opted for, and at considerable cost relative to other resins.