"Alternative Mold Materials for Organic Black Rubber Molds" Topic

I need to make up some new molds so went to Contenti to purchase some 700 Series Black Organic Rubber 9" mold blanks only to discover that such is no longer available. A call to Romanoff provided the info that the only manufacturer of black rubber for molds had shut down last year. Silicon rubber seems to be the only alternative. My question for you professional casters is what material are you using? From what source (USA)? I am casting 94-6 Tin alloy running it at about 610F. Any help would be appreciated. Thanks.

Jeff

Having the same issue and after doing homework realized the chance for U.S. moldmakers to get organic rubber are slim to none, I used pink silicone from Omar's Workshop in CA. Omarsworkshopllc@outlook.com

We have the same problem!!
We use 100s of molds a week !!
Silicone tears much quicker and does not last
Russ Dunaway

Well, I may have gotten the last of their stock when I ordered in January, as I only got 70% of my order.

I've used silicone molds in the past and they retain heat longer, get brittle quicker and tear easily. Another factor that will eventualy increase the cost of doing business.

Dave

I suspect that the profit margin on silicone is much better than on black rubber?

martin

Well it does not sound as if there is a really good answer. I tried a silicon mold once and did not like the results as it warped and ended up curling badly. I was told that I had probably abused it by running it too hot. The info I was given was that you only allow the metal to spin in the mold for about 20 to 30 seconds then de-mnold the sprue, lay the mold open on a flat surface with a fan blowing air over it to cool it back to near room temp before you spin it again. I guess I'll try a few types and see what works.
Thanks everyone for your comments.

I tried a silicon mold once and did not like the results as it warped and ended up curling badly. I was told that I had probably abused it by running it too hot.

Silicone moulds curl if the outsides are cooler than the insides. It's down to expansion/contraction at different temperatures (the cold surfaces of casting machine plates will cool down the outside of the mould). Organic rubber tends to keep its heat better and is less prone to the curling effect than silicone; because it retains heat, it also tends to overheat faster.

By prewarming silicone moulds and operating using a warm stack of four to five-plus moulds, you can in effect reheat the outsides of a freshly cast mould while you de-mould and cast from the others (the warmth from the other moulds reheats the outer surfaces). Running silicone moulds from cold will give a more pronounced curling effect. I always cast with prewarmed silicone moulds. They cast better, and they expand to nearer what was their original size in the can, reducing the effects of shrinkage.

All rubber tears easily. Undercuts will kill black rubber moulds as readily as they do silicone. And if you want to see brittle, cracked moulds, you should see some of the black rubber ones that I have retired from the Gladiator Miniatures line. :-)

It will effect prices!
Our molds went up $11 USD per.
Now, multiply that by 60- 100 molds a month?

Regards
Russ Dunaway

I learned about this happening several months ago and believe me it came out of the blue. Conley Casting in Rhode Island closed without notice apparently. I had be a customer of theirs since the 1970's and I did not receive any pre-notice. Simply put, Conley made, by far, the raw black rubber sets used by those in the jewelry and while metal casting trade. Contenti – also in Rhode Island and also a huge supplier to the trade took over all aspects and stock of Conley's including their phone numbers, but not the black rubber making operation. I believe Conquest Industries in California also used the black rubbers manufactured by Conley – but now I believe they have gone out of business or have stopped for some reason. (Conley made the rubber sets on their premises in Warwick RI on a large machine which I once saw in operation. We called it the million dollar machine.)
Now – and until who knows when – no more black rubber is available for open purchase. There are silicone based sets appropriate for ‘some' white metal casting, but I disagree strongly with anyone professing they are an adequate substitute for black rubber sets. Silicone costs more – WAY more in some cases – is not as tough and flexible in use as black rubber vulcanized sets, and will go far to change things dramatically in this hobby.
I'm certain there will be more coming down the road about all this and how it will ultimately affect our great hobby.
Toby Barrett
Thoroughbred Figures

Sure silicone is readily available, but at 2 – 3 times the cost of black rubber. I would be willing to pay the price, but the real problem is undercuts.

Wargaming figures often have deep undercuts, especially horses and humans with weapons. Armored vehicles with bogey wheels, ships with tripod masts, you get the picture. A large dragon's head with big rows of teeth would be hopeless. Silicone just can't handle them like black rubber.

Contenti took over the black rubber trade of Tekcast and Conley, became the sole supplier of said rubber, then discontinued it. Thanks a lot, guys.

And to make matters worse, if anyone has a large supply of black rubber, be sure to use it all in a timely manner because it starts to go bad after a few months.

Can anyone in Nottingham (or anywhere else) offer any assistance or advice? Who is the biggest seller of black rubber in the UK?

That all sounds a bit grim.
Im in the UK and I get my moulds from Coker and excellent they are to.
j-coker.co.uk/casting-discs

L
Adler Miniatures

I sent them an email this morning and received a reasonable quote for black rubber sets within the hour. Even with a hefty shipping fee, the total price was still much better than Contenti's best price for silicone.

Thanks Leon!

All I can add since my posting five days ago is that the problem is being ‘worked' – from reliable sources – here in the states. No idea of when or how. When and if I hear more I will post again but I'm only in intermittent internet capability.
Toby Barrett

Tumbleweed, your welcome.
L

Has anybody tried this new stuff?
link

I have not. Yet. And may have to. ‘Nicem' has been around awhile in several colors for different applications so it is not new. I am very skeptical about the claims of the black type being a ‘suitable' alternative or replacement for organic (petroleum based) vulcanizing rubbers. From my last invoices from last year the organic type was approx. $13 USD for a 9" x 1" set. At three times the base price of that I am doublely skeptical – almost a cynic that Nicem is a viable substitute.
I still hold out hope that we will ultimately have an American based supplier of the old stuff – or very near to it – and intend to make repeated inquiries until if and when we do.

I made some from silastic liquid gasket mixed 50/50 with talc powder.

Came out like dough.

Did work, not perfect, but I hand pressed, so a mechanical press would help.

Just an idea, no idea about price comparison, but basically half a tube cost due to near free talc cost.

I used 1/2 a tube per side of a 6" mould, so 1 tube per mould.

Could be a time to think outside the square and spend a weekend giving a few alternatives a crack.

Also, as I believe the typical moulds are soft and putty like?? What about adding cut up or grinded old mould as a filler.

They use grog in clay and pottery, which is just broken up fired clay mixed with fresh clay.

Also it's done in RTV silicone casting, using cut up bits of old moulds to fill spaces in master moulds.

For example if your making a lot of spears or shields, anything flat, why not slice the moulds in half, so it has a fresh interior sandwiched between an old recycled exterior?

You could cut the old mould in such a way as to allow the fresh mould to lock into it. Maybe cone shaped holes that fill with fresh material creating a lock.

Or if there's gaps between things in the mould, just cut out chunks and push in chunks of old mould.

The fresh chunks can later pressed into a mould shape for use.

Or just mixing fresh with ground up old mould, to be tested.

Even cutting chunks and adding chunks of metal/ceramic? What have you. But rubber may be best.

Or what about making 3 piece moulds, stack 3 layers with 2 layers of figures? One poured from one side, the other from the other side. Sounds crazy, but should work??!!. Saves you half a mould. Life expectancy may vary, the centre layer would cop it worst. Would certainly suit lower volume expectations or even master moulds.

A great time to experiment and think of crazy ideas.

Also what about uncured tyre rubber??

link

Were these guys mentioned?

It says its made in the US.

H Man,
In a way, yes, they were mentioned. TekCast was originally in CT I believe, but my memory may be faulty on that. Their operation, products and in one case an employee (Ron Abato) was folded into Conley Casting in RI. Both Conley and TekCast in turn – as we recently discovered – were incorporated into Contenti. I believe both TekCast and Contenti originally sold organic rubber sets under their own respective names but it all came from Conley. (I do know for certain the Contenti rubbers came from Conley.)
If you go back to your TekCast link and hit the home button it will take you to the Contenti takeover message. So TekCast is no more.

Sorry H Man,
Just learned you are in Australia so I'll write out my abbreviations.
CT is Connecticut and RI is Rhode Island both in USA.
Rhode Island, parts of southern Massachusetts and industrial areas of New York City and Connecticut used to be the costume jewelry capitals of the world; speaking here of the 50's, 60's and 70's. Contenti, Conley, TekCast and several others I could name were all mainstays and suppliers of machinery and materials used in the trade. It's all dispersed around the world now for the most part.

Good point.

I believe steel bolts, hand tools, and such like are also spin cast.

With a lot of that going overseas, it may also have an impact on mould supplies. Though they may use higher temp silicon?? They nodoubt share supply chains.

I wonder if natural rubber sheets are available from some other industry. The discs are probably die cut from them. Is there any information on why natural rubber is no longer available?

link

3/4 of world production of national rubber is used to make tyres.

As I touched on above, perhaps there is a solution.

I believe retreads are vulcanised, as are whole tyres.

Perhaps start with a local tyre repair place and work your way up to someone who sells the rubber.

I'm sure there may be differences in composition, but either it may work fine or the supplier may be otherwise able to get what you need.

It's called a phonebook.

Perhaps get an old tyre. Cut out two chunks a few inches square (a tyre shop with a mountain out back may oblige).

Cut a shape and inlet, what not into one piece, sandwich with the other in a vice, heat some metal and pour.

Post the results.

"Revulcanized rubber is essentially taking recycled rubber crumbs that have been devulcanized and vulcanizing them all over again,"-greatmats

"Vulcanization, in common with the curing of other thermosetting polymers, is generally irreversible."-wikipedia

Isn't Google great.

Greatmats link:

link

Rubber links link:

link

So perhaps, with further research, you may be able to devulcanize old moulds, then revilcanize them???

A few thoughts:

Bet you wish you didn't throw out all your old moulds.

Perhaps an easy method to try is to granulate old moulds, perhaps slicing off surfaces first to get only the cleanest rubber.

Then chop finely or grind up the moulds.

Next get a fresh mould (I know, I know), and mix in an amount (???) of granulated old mould.

The result should work. Perhaps slice a fresh mould to lay a thin slice directly over/under figures to ensure details.

Worth a try.

I'd assume it may not be as durable??? But should work???

Perhaps rubber car tyres, or better yet tubes, which are easier to cut and cleaner and no wires in them; could be granulated instead of old moulds???

It didn't take much time on google to find this: PDF link

Interesting.

It doesn't specify mould making or any hot area use.

I wonder if the 20-70 degrees is for vulcanization or later use?

But could be heading in the right direction.

An email to the company could clear up any questions.

Also remember some people pour resin into moulds, so different rubbers may still suit.