Vinamold and mold making in general

[ryoden]

I was considering making my own molds for dungeon (and other floor type) tiles, corridors and rooms etc.  I have never looked into this before so was searching on google.

I found a couple of "reusable" mold making materials, one only seems available in the US called Composimold and another cheaper product that is available in the UK (where I live) called Vinamold.
http://www.maragon.co.uk/vinamold.html

I was wondering if anyone has had any practical experience or knowledge of either of these materials as I have heard good and bad reports but they were generalised.  I was interested in the reusable material since I thought it would be less expensive for someone starting out (when you make most mistakes).  I am interested in comparisons with more standard mold making material like silicone RTV, which is 2-3 times as expensive and not resusable.

[Dewbakuk]

Vinamold requires a good heat control to melt it. I've got some but whenever I tried it I burnt it.

[Heldrak]

Why not just use Hirst Arts molds...?

[Svennn]

Vinamould sounds very much like Gelflex which I have had varied success with. The re-useable aspect appealed to me too but like Dewbakuk I have burnt the stuff on more than one occasion. I am a real tight wad stingy bugger but have to admit RTV is the way to go.

[ryoden]

Why not just use Hirst Arts molds...?

I have looked at them but they appear to be 25mm and I want to use 30mm+ bases, also I just wanted to use my own designs as practice.

[ryoden]

Vinamold requires a good heat control to melt it. I've got some but whenever I tried it I burnt it.

Vinamould sounds very much like Gelflex which I have had varied success with. The re-useable aspect appealed to me too but like Dewbakuk I have burnt the stuff on more than one occasion. I am a real tight wad stingy bugger but have to admit RTV is the way to go.

I see, I had heard that was an issue although I did read that you have to heat it slowly not to burn it but I assume that you did that and it still was difficult to use?  It appears that in this case I may have to go with the normal RTV.

This is from one of the sites i looked at
The more care and control exercised in melting vinamold the more times the material can be re-used. Thermostatically controlled melting equipment is available but a heavy pan used on a carefully controlled hob or in a suitable oven, etc is the usual method. For small projects (say, less than 1kg of material) the rubber can be melted in a microwave on a low setting, however constant observation is required throughout to ensure no overheating - the material only needs to be brought to a liquid state, and no fumes or discolouration should arise, as this is an indication of decomposition.

Thanks for the replies so far

[Dewbakuk]

I've tried both the microwave and the hob. The problem I found was that when it starts to melt you have some of it running off while the rest is in lumps, much like when you melt butter in a pan. Unlike butter however, it's difficult to keep the rubber moving to prevent the burn and while you're messing about with the lumps, the runny bit burns.

Should I ever get around to trying it again, I think melting it in a banmarie would be the way forward, the way you melt chocolate.

Like Svennn however, I just use RTV these days.

[Svennn]

I have had success on a hob after spending an absolute age cutting the blocks into very small pieces but until you come to do it you dont realise just how awkward/difficult it is to pour boiling hot rubber anywhere let alone a small mould. Also as I often use plasticard or rod in my masters it is not suitable.

[ryoden]

OK thanks I think I am convinced that this is going to be way more of a problem than it seemed at first glance.  I guess I will go down the RTV route instead.  Does anyone know of a good deal on RTV (or anything that does the same job) in the UK or are they all roughly the same price?

[snitcythedog]

I am a real tight wad stingy bugger but have to admit RTV is the way to go.

I think melting it in a banmarie would be the way forward, the way you melt chocolate.

RTV is the way I go too.  Dewbakuk's suggestion of using a double boiler looks sound for this material.  It would defiantly control the burning issue and allow it to evenly heat.  The only question that I have is how would it react to steam?  Sorry I cannot help you with the RTV question as I am not in the UK.  Good luck.
Snitchy sends.

[Connectamabob]

I've used rubbers like this for casting Halloween props, though not for mold making. Everything that I read beforehand seemed to indicate that while it was technically possible to do it in a pan, attempting to do so was fussier and much more prone to burning than other methods. I think a lot of people sucker themselves into doing it this way because it seems simplest & easiest, based on the equipment, when in practice it's actually the least simple & reliable when you factor in the level of technique needed.

Double boilers are supposed to work well, though I haven't tried one myself. The trick IIRC is to use oil in the boiler instead of water. No steam, and it allows you to get a higher stable temp than water.

I used an oven. I have a "shop oven" in the garage I use for non-food safe art/craft stuff (just a $40 countertop turkey roaster oven from Costco). Put the rubber in a Pyrex measuring cup, and set the oven temp to just above the melting point, works like a charm.

All that said, I also gotta recommend using silicon instead. Yeah, it's more expensive, but even with a good melting method, this stuff has too many fussy aspects to make the cost difference worthwhile IMO.

[zizi666]

   Oil in a bain marie, that's crazy ! 
the whole point of bain marie is that it maintains at 100°c (as boiling water turns to steam and escapes.)
Now with oil you can go much higher and risk a fire.
There's a reason why there are thermostats on deep frying pans !!!

[Connectamabob]

That's half the point, actually. The melting point of the rubber is significantly higher than the boiling point of water (the stuff I used needed about 175°c), so you need something that can get a lot hotter than water in order to melt it in a double boiler.

The main purpose of using a double boiler to heat the rubber isn't to cap the temp, like it is with food. It's to get a "softer" more even heating than a bare pan, thus preventing situations where some parts of the rubber begin to burn while other parts have yet to melt. As with a regular pan, you'd cap the temp manually by measuring and adjusting the flame/electricity. You'd want to choose an oil with a flashpoint that's higher enough the rubber's melting point to give yourself a decent safety margin, of course.

But if that sounds like a messy pain in the mivvonks to you... well it did to me too, which is why I never actually tried it. The oven method I decided to try first worked out so well that I never needed to faff about with anything else.

But I stopped using hot melt vinyl a long time ago. Silicon's easier to cast, easier to paint and color, you don't have to use special mold materials or take special safety precautions to account for high temperatures, and the finished product doesn't leech plasticizers that can melt styrene or mess with your endocrine system. That's well worth the extra few bucks.