"Alumilite HS3...*thumbs down*" Topic

Okay first off let me say that I LIKE Alumilite Quick Set RTV molding rubber…
However for some stupid reason my local store has stopped carrying that and has started carrying HS3…and only one box of it per week…they never order 2-3…just one…even though I ask them.

Over the past few months, I've attempted four different molds with HS3…Either I am a total complete blithering idiot, or this material is not as user friendly as the Quick Set.

First off, you have to stir the compound rubber to mix it up..and it takes a good 10-15 minutes of hard stirring to get it all properly mixed…If it's been sitting for longer, then the stuff is going to be harder…

Then for a complete kit pour you add the entire of bottle of catalyst (after shaking) and stir again…It looks like pink dishsoap coming until you mix it, and then it turns pinkish grey.

Then you pour…

I've attemtped to do 2 15mm molds (one out of wood, and one being a resin FoW British Lorrie to see how it works on different substances…
Both 15mm molds were failures.
The cure time is supposed to be 18-24 hours…in the case of the truck, it was 2 1/2 WEEKS!
After the molds finally dried, (they remained a pinkish sticky goo, like bubbelgum), for over a week, I tried to get the trucks out of it..and failed…the molding material had basically become a gooey compound. I ended up cutting the trucks out, and right now they look like they hit a bubblegum factory.

The 28's are just as bad…

I've gone over and over the instructions, measuring, etc…for HS3, and each time, the process ends in utter failure..

So I guess if I stay with Alumilite it will be Quick-Set stuff for me.

I'm wondering if anyone else has any similar experiences, or knows what might have happened?

And can anyonse suggest a good alternative, (that's available in the US?)?
Thanks…

Never had much luck with alumilite. Even the molds that I got to come out fairly well usually started to fall apart fairly quickly.

I prefer the tried and true. Permatex high temperature red rtv and ez release 800. Usually works pretty well, and never any gooey mess. The few molds that have failed I just breake the figures out and start anew.

Murphy,

I highly recommend this e-bay seller.
auction
Just write a message telling what you want to do and he will send you the right stuff. I have his 10 to 1 RTV. It works as advertised.

Murphy, Sorry to read of your problems, but interesting to me, as I use HS3 extensively, and haven't had a problem with any of their line of RTVs in probably 15 or more years making molds ranging from a few ouces to around 50 pounds.

Amazingly enough, it sounds like you did not get a good even mix during the stirring process. With small quantities, I aways hand stir it with a small flat piece of wood or plastic, making sure to scrape the bottom and walls of the container. I do not scrape out every last little bit of rubber in the the container as the residue on the walls and bottom will not be mixed and will leave soft or sticky spots in your mold. Stirring usually taks 90-120 seconds, with the material having a consistent pink color throughout. Any variation in color means that it is not stirred thoroughly.

If you had to stir it prior to adding the catalyst, something was wrong with the RTV. It should not be particularly hard to stir at any time (unless the shelf life had expired), being like a thick pancake paste. What you describe sounds like the consistency of bread dough. I've been using their RTVs (HSI/II/III, 3120, 3110 and others) for two decades and have never seen the RTV settle out or need mixing.

Note that the RTV has a 6 month shelf life from the manufacture date, and becomes stringy and hard to stir sometime after that. I have used RTV that has exceded its shelf life, but it takes a little extra care, and I avoid masters with lts of surface detail and/or deep undercuts. Shelflife can be extended buy storing in a cool place.

Also note that sulfur compounds can react with the RTV, so using colored clay in mounting the master is a no-no, and some finishs or materials in the master could cause problems. Usually the problems manifest with the RTV in contact with the sulfur not curing.

Rubber not curing in 2.5 weeks is either a mixing problem, a shelf life issue, or a defective product problem. If you are degassing the mixed the rubber in a vacuum, you can remove the hardener if you leave it in vacuum for too long.

I would contact Alumilite about it, and see what they say. I would also look into buying fresh material direct from them. They will probably refer you to the source that you used, but I would explain that after your experience, you will go to another product, rather than risk buying "expired" RTV again.

I too suspect it's may be shelf life issue. I have bought rubber/resin products directly from Micromark and they work just fine. But if I get the same items from a local hobby store they are often defective even though I am using the same techniques; the difference could simply be that in the latter case they have already been sitting around, under sub-optimal environmental conditions, for a few weeks or even a few months when I bought them.

What I find odd are the instructions that I read on an Alumilite pack in a local store – they are in terms of weight, yet volume would probably be the easiest measure for most hobbyists…

I quit using their rubber and only use their resins now.

Inquisitor Thaken,
What is EZ Release 800? Do you use the Permatex for metal molds?
I think the Permatex would have to be thinned some. I experimented with low odor mineral spirits as a thinner for the Permatex. I was pleased that the Permatex still set. Though I have not tried a mold yet.

Definitely sounds like 'past use by date' for that product. I know of several other RTV's that have definite 'use by' dates, either the rubber or the setting agent go 'off' – in one case the 'catalyst' ate the bottle it was in & ran out all over the shop floor – about 3 litres (over 1/2 gallon) of blue goo.

I have however used Dow Corning 3110 after several years on the shelf & it still set up fine – the white pigment/filler – actually diatomaceous earth – had settled out & was a PITA to stir back in.

castellan "What is EZ Release 800?"

A release agent, made by Dow Corning.

"Do you use the Permatex for metal molds?"

Yes.

"I think the Permatex would have to be thinned some. I experimented with low odor mineral spirits as a thinner for the Permatex. I was pleased that the Permatex still set. Though I have not tried a mold yet."

You cannot try to use it as a liquid. This won't work. Instead, it has to be pressed in around the figure, after the release agent has been applied, and with the figure pressed half into a bed of playdoh. When the whole thing hardens, you wash away the playdoh, and now you have your mini sticking in half a mold. Now you spray this half (and the figure, of course) with the release agent, and, again, press in the permatex rtv around the figure. When the whole thing hardens, you have a two part mold. The hardening process takes about a week, during which time you have to keep the permatex mold immersed in water.

There are a lot of additional nuances, but those are the basics. Hope that helps.

This may be a silly question, but was the proper catalyst supplied with the RTV…?

Inquisitor Thaken,
Thank you!