Resin casting - the view from here

Tom Madden

I’m feeling particularly reflective and aware of my own mortality after Sunday’s bittersweet celebration of life for my late wife, and want to set down my thoughts on the history of resin casting in the hobby from my viewpoint as a long-time resin caster. I apologize for the length and beg your indulgence, and hope this will add to the record rather than confuse it.


Tom Madden


In my Bell Labs career (1960-1994) I was fortunate enough to be awarded a number of patents. Each was the result of my perceiving a need, solving a problem, or seizing an opportunity. I'm proud of those patents, but the reality is, the needs, problems and opportunities were there for anybody, and if it hadn't been me, it would have been someone else. Most likely sooner rather than later. It's important to separate the true innovators from those whose contributions are founded on the work of others, or who just happen to come along at the right time. ("When the student is ready, the teacher will appear.")

Bill Clouser was certainly an innovator, but for me it's because of his articles on using Strathmore papers for modeling. (The Strathmore Story, MR, February & March 1959. Later that same year another innovator, Al Armitage, had his landmark articles on styrene modeling appear in MR.) By the mid-'60s a number of us were, as Dennis mentioned, using tooling resin (epoxy) to cast parts in silicone rubber molds for personal use. Bill's casting was the ultimate expression of that technology, and his work was superb. Problem was, epoxy is a very aggressive casting medium and you'd be lucky to get 6 or 8 good parts from a mold. I was making some very nice HOn3 parts using Ren and Ciba-Geigy epoxies, but cost wise I couldn't compete with brass parts, let alone with Grandt Line plastic parts when they came along. All credit to Bill Clouser for seeing the bigger picture and being the first to offer commercial cast resin parts, but he wasn't the only one using the technology at the time.

The true innovator for resin casting in the hobby was, at least for me, Jack Work, with his March 1961 MR article on cold detail casting in rubber molds. He used Devcon Liquid Steel, a thick, solvent-based putty-like material available in both tubes and cans. You'd squeegee it into an open faced mold, smooth the back, let the solvent evaporate, and 10 or 15 minutes later (for small parts) pop the now-hardened part out of the mold. About the time Jack's article came out a rep for either GE or Dow visited my lab to show some new semiconductor potting compounds. One was a liquid rubber material which didn't need heat to vulcanize, you just mixed two components together and it self-cured. They called it "Ready to Vulcanize" or "RTV" for short. The rep left a pint sample with us, a coworker glued a nickel to a glass plate and with cut-up tongue depressors made a little box around it. We mixed up some of the new material and filled the box with it, came in the next morning and melted some Woods Metal (a low melting point alloy like CerroBend) and poured it into the mold cavity. A half hour later, using a mere $5 worth of Woods Metal, we had a dozen single-sided cast metal nickels to play with. (In retrospect, the economics of that were about the same as for my later cast epoxy parts.)

We eventually threw the cast coins back in the melt pot, but that weekend I went to the hardware store and bought a can of Liquid Steel. The HOn3 market was served with brass parts by Kemtron, Balboa (under the Slim Princess label), and an outfit in Texas called Slim Gems. I was building a bunch of D&RGW HOn3 box cars, passenger cars and cabooses using Clouser's layered Strathmore construction technique and needed lots of detail parts. Availability was the problem, not affordability, so I proceeded to duplicate everything from coupler pockets to truck side frames with Liquid Steel following Jack's article. Even made some two sided "squash molds" for doing side frames so I could incorporate the bearing holes. (Liquid Steel had a component which made it self-lubricating so the bearing holes didn't wear.)

The cold-cast Liquid Steel parts were hard and looked good, but they had hardened by drying, not by curing, and lacked cohesive strength. Great for surface details, not good for structural parts. This didn't become an issue until 1964, when in the course of re-detailing one of my two PFM HOn3 K-27 locos my pliers slipped when I was attempting to remove the number board and I gouged a smiley face into the smoke box front. I was horrified and terrified - we hadn't started a family so Gail was still working, but I thought I had destroyed a model that had cost over 10% of my monthly pre-tax income! It took a week or two before I could consider the problem rationally, but I ended up completely unsoldering all the parts of the other K-27's smoke box front, making an RTV mold of it, and casting duplicates - not from Liquid Steel, but from Ciba's Araldite potting compound. Araldite was a clear epoxy so you could see any entrapped bubbles. Slightly heating the mix reduced the viscosity enough for the bubbles to float out before it "kicked". Much to my relief the replacement smoke box front was a perfect reproduction. So much so that I also duplicated the headlight, headlight bracket, number board and marker lights in Araldite.

So my casting experience started in 1961, and my resin casting in 1964 in a clear case of necessity being the mother of invention. I gave up on epoxy casting before we moved to Colorado in 1970, and never did any casting for the rest of my HOn3 days, which lasted into 1986. It was all personal so I make no claim for being a contributor, let alone an innovator. But it did give me a considerable advantage in experience and insight when urethane resins came along in the 1980's.

I'm not exactly sure of the timing, but it was after I'd abandoned HOn3 modeling, after I'd discovered the articles by Dennis, Richard and Al that continue to inspire so many of us, and clearly after the introduction of Al's and Dennis' kits. At a printed circuit manufacturing trade show in Anaheim I found a company, Conap, offering a new resin that claimed many advantages over epoxy - not as an adhesive, but as a casting and encapsulating material. It was, of course, urethane resin. I gave them my card ("Advanced Printed Circuit Laboratory Supervisor" - a title much more grand than the position, considering I supervised only six people) and asked if they could possibly send me a sample. I must confess to ulterior motives - I had no use for the resin in my lab, but I knew, as Dennis discovered several years prior, that this was the casting material I had been waiting for. A week later a package arrived containing two one-gallon containers - one each of part A and part B to be mixed 1:1 by weight - and a spray can of mold release.


Imagine my delight, after those early epoxy casting days, of being able to get 30 or more parts from a mold. Those two gallons of material lasted several years, during the course of which I began an extensive correspondence with Richard Hendrickson and, instead of building his WestRail PFE R-40-23 kit, made all the mods and converted it into a set of patterns for flat casting. In May 1994, two months after I retired, I drove out to the UPHS convention in Ontario, CA, bringing with me a multi-panel display of the R-40-23 showing all the steps from pattern making to finished model. The last panel read: “Gnash teeth in frustration when InterMountain announces injection molded plastic model of the same prototype”.


A year later I literally fell into the opportunity of a lifetime when a former neighbor, seeing my hobby casting setup, insisted I join his newly-formed rapid prototyping company. I stayed for 21 years. Experience in that field, now known as 3D printing, exposed me to industrial resin casting in all its glory – multi-part molds, vacuum assisted mold filling, pressure curing, heat treatments, rigid and flex resins and all that. I couldn’t wait to bring it to the hobby. With more enthusiasm than it deserved, I brought it to the attention of Al and Martin, then later to Jon Cagle, two potential resin casters for Ted, Gene Fusco and Aaron Gjermundsen. Al, Jon, Gene and Aaron were success stories, the two for Ted not so much. And Martin, while declining to add closed mold casting and one piece bodies to his personal skill set, was successful in conning convincing me to cast some 1500 tank car shell sets for Sunshine.


Am I an innovator? I don’t think so – more of a facilitator. I’m certainly pleased with the contributions I’ve been able to make, but as with the patent example back in the first paragraph, if it hadn’t been me, it would have been someone else. I’ve also been in the right place at the right time, a number of times, and am not unaware of the role luck has played in what I’ve been able to do and experience. It’s been a helluva ride.

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