For some time now, I have wanted to build some freight house structures, and the Walthers Cornerstone Modulars kits are ideal for this purpose. Trouble is, they have been long discontinued and the kits are all but impossible to find even on eBay.
Recently, a fellow forum member, RR_Mel, encouraged me to try my hand at making rubber molds and then casting the necessary parts with resin which is a form of plastic (sort of).
I thought that I would share my experiences with others on the forum and encourage them to give this model making method a try.
Silicone Rubber Molds
Following Mel’s recommendation, I bought a starter kit at Hobby Lobby using a 40% discount (readily available from several sources) to purchase a $30 kit for only $18. The kit is manufactured by a firm called Alumilite, but you can buy rubber molding kits from several different manufacturers.
The mold is actually made from a liquid silicone rubber base and a catalyst used to harden the mix into a rubber mold. The mixing ratio is 10:1 rubber: catalyst. You need to be precise, so I use a small food scale to measure the volume of each component in grams.
Gerry Leone just had a MRVP video about using blister packs, the clear plastic that covers a cardboard package that contains, well just about anything you buy these days. He did not go into the molding process at all.
Is it hard to get the right thickness and an even thickness, for instance the window frame?
Not hard at all to get the right thickness. Just needs to be a little deeper than the object to be cast. What is critical is to set the mold container on a level surface.
I did that window frame face down. Worked like a charm.
I’ve made lots of silicone molds and cast resin parts over the years using my own masters that I made from wood or styrene. My nephew worked at a place that had a vacuum chamber that he could use. That eliminated any bubbles in the silicone.
By placing the part detail-side down it might be tough to get trapped bubbles out?
As a side note—You could potentially be stepping into copyright infringement territory by copying someone else’s (Walthers) proprietary property.
I believe Chooch became aware of the shrink-wrap duplicating and as a result they now place a slip of paper on top of the part before packaging it.
I’m just mentioning this as a friendly “heads-up” as some manufacturers may not take kindly to their work being duplicated [:O]
Ed, you raise an interesting point, but I would ask two questions in reply.
These pieces are being replicated for my personal use so where is the issue?
These kits have been discontinued so Walthers has made it near impossible to find and purchase them, so what would be the objection to casting them for personal use?
In fact, wouldn’t most mold making / object casting face similar problems since almost all castings are of someone else’s product?
Fair use is still a thing. You could spend the rest of your life making rubber molds and resin clones of everything you own. It isn’t a problem until you sell one.
Our entire hobby is the hijacking of someone else’s intellectual property, to a degree. Fair use is what gets us through.
Also, you may recall that in the April 2009 issue of MR, an article described how to use DPM wall sections as masters to make a part. While DPM didn’t make a part like the one depicted (a single window panel), parts of two DPM wall sections were used as the components of the master. If this part had gone into production in someone’s garage, it would constitute infringement of DPMs intellectual property. But, casting a few parts for yourself, there’s no issue at all in the slightest.
“If there is no money there is no lawsuit.” said my business law professor. But as soon as you make a buck off of it they are entitled to 3 times (I think) what you made and your inventory has to be destroyed.
However lawyers don’t work for only $3 so they won’t get involved unless there is sufficient money for them to have. It’s all about the money. If the company already has lawyers on the payroll they may send you a cease and desist order. If you are selling on eBay it is a violation of your user agreement and if someone complains then eBay will boot you off if you continue after being warned.
Also state and federal laws do not apply to most foreign countries unless we have it written into trade agreements and even so they are hard to enforce unless the company has people in that country. Those cheap figures (people) from China on eBay are made from Preiser figures. I don’t know if they are legally licensed by Preiser nor do I know if Germany has trade agreements with China. If you negotiate ahead of time and license the product you can make and sell other people’s stuff. Think about Columbia House and BMG record clubs. They had licensing agreements to sell all of those CDs, records and tapes which they printed themselves.
I only bring it up since I recall the recent controversy over some guy DBA “Big Dawg” or some such moniker. He was “allegedly” making revisions to diesel shells, using parts from other manufacturers, then making latex molds and resin shells and—yes—selling them. In his case I am completely against his use of masters that Athearn, Rapido, Bowser and others have invested huge amounts of research, time and expense to tool and manufacture.
I know your goal is to make parts for personal use with no intention of profiting from it. My only reason for my post was to caution you that there might be a few eyebrows raised over using a Walthers part as your master then showing everyone else how to do it on a public forum.
The law can take some pretty crazy turns when it comes to copyright and I’d hate to see you caught up in something that had very innocent beginnings.
OK, this thread has taken an unfortunate turn because my only purpose, initially, was to discuss the use of rubber molds and resin casting. I just happened to use Walthers Modulars because I have some on hand so I used them as an example.
At this point, I see no reason to continue this thread so I will ask Steven Otte to delete it.
But, let me close with this comment. I probably have purchased over 100 various kits from Walthers during the past several years. In fact, being a pack rat, I still have all of the boxes. In anticipation of an upcoming project, I have recently purchased even more kits from various retailers and on eBay. But they have become increasingly difficult to find, since the kits have been long discontinued by Walthers. I have no intention to sell any castings or to make any for fellow modelers. I simply needed to create some additional parts to finish the project.
You did a beautiful job on this - both the actual molding and the “how to” description. As you said, this is all for your own use and your intent with the thread is to share your experience and view on the subject - which I for one appreciate.
The legalese has been noted and acknowledged. As it is certainly not a factor in your endeavor, hopefully it will be put to bed. Please continue with the thread to the actual use of the castings in whatever structure you are building!
I think you may be overreacting a bit to the copyrite issue. You are not doing it to make a profit. It is for your use only. That is the crucial point.
I strongly disagree with deleting the thread. Your tutorial was excellent.
I agree with the ''critter"…You also did a fine job on Your presentation!
As a side note? Don’t You have to coat some sort of release agent on the part before inserting into the wet resin? I did some moon’s ago and had to coat them with a slippery talc like powder before inserting. Unless things have changed.
Take Care! [:D]
Frank
EDIT: Could also be My memory…It’s been a long time…LOL
The how-to knowledge Rich is sharing in this thread isn’t a big secret. As someone above already noted, we’ve run articles in our magazine on how to make and duplicate modular wall sections in resin. So nobody’s enabling a criminal enterprise by telling people how to do this. It’s kind of like the argument the TV and movie industry made against videotapes when they hit the market. It’s not the method or the technology that’s wrong, it’s what one chooses to do with it. Since what Rich is doing with it – duplicating almost impossible to legitimately obtain parts for his personal use only – is legit, so is this thread.
Now that that is all out of the way, there’s something I got thinking:
How do you plan to insert the window casting as you don’t have the small recessed area around the window opening? Perhaps it would make sense to make a variety of assembled wall panels with windows inserted and use those as masters?
OK, thanks Steven. Let’s keep the thread up then, but please understand that I am not encouraging anybody to do anything wrong here. My main purpose is to cover some basics on rubber mold making and resin casting. If kits were still available from Walthers, I would have purchased them and never even thought of casting. Used appropriately, mold making and casting can be a legitimate solution to a modeling problem.
Frank, things have not changed. The use of talcum powder is still recommended as a release agent. Also, some of the molding kits include a bottle of liquid release agent. I skipped this step and had no problem removing the cured casting. But, that may be because the object being cast is thin and flat. It may well be that some sort of release agent may be essential for larger, three dimensional objects.
When I made my very first mold, I did what you suggested, I glued a door to the inside of the wall section and laid it face up and then poured the silicone rubber mix over it and that worked just fine. However, that seemed more problematic for the window in the wall because if laid face up, the liquid rubber would fill the window openings. And if I inserted the window into the wall section and cast it face down, the liquid rubber will not reach the recessed window. So I had to do the windows separately, face down.
I haven’t yet glued the windows to the wall sections, but they seem to fit just fine. One thing that I did not mention is that when you pour the resin mix into the mold, try as you might, it is hard to fill the mold precisely without overflow. So, what I have been doing is using a piece of styrene sheet to “scrape” off the excess before it starts to cure. That results in a very flat back on the cast wall section or window or pilaster for that matter.
