Re: [SGII] Modular Starship Terrain AND CASTING

The plaster I have here is labelled "LePage's - Poly - Plaster of
Paris".
I've done plaster terrain bits, and it's worked fine.

My caveat:  don't bang them around too much.  They will take some abuse,
such as found in normal play and decent storage.  If you toss them off a
table onto the floor, they *might* break or chip.  If it cracks, you can
glue it and repaint - not difficult.  If it shatters, well, make another
one.

These are *not* as strong as a cast resin piece, but a *lot* less
expensive.  I'm satisfied trading off the strength for the cost, and
then
taking a bit extra care in the "care and feeding" of my terrain.  If
your
wall sections are really thin, you might want to stick to resin, OR use
a
reinforcing method such as glass fibre, plastic mesh (like you'd use for
a
window screen), gauze, etc.  That will at least stop the part from
shattering all over the place if it drops from too high up or at a funny
angle.	Also, as I said before, depending on the size of your piece, the
plaster sets up to a point that you can demould pretty quickly.  While
I've
got some odourless 2 minute resin, that stuff costs a bundle.  Some
other
non-stinky resin I've used in the past is great and available in large
quantities, but is pricy and takes up to 24 hours to setup properly
(unless
you boost the reaction by cooking it, but that's tricky to do properly -
you have to use a hot-air "oven" or the temp gets too hot).  And there
are
resins available like polyester resin for fibreglass, commonly available
all over the place, but it stinks a LOT to use and is hugely toxic.

The plaster hardens with an exothermic reaction, but won't get hot
enough
to damage your moulds unless you have unusually soft RTV (or RTV with
*lot*
heat tolerance) UNLESS you make huge parts that are very thick masses of
plaster.  Then the heat can build to dangerous levels.	For the kind of
stuff you're talking about, you won't have a problem.

I just bought a couple of pounds of Polytek - Plastil 71-30 Silicone RTV
and it is heat-rated enough to work with melted lead, so for plaster
it'll
be fine.  I imagine that is going to be common to a lot of the stuff
available.

This assumes you don't have an inside line on some good cheap resin, of
course.

And if you use some kind of mould-release, it can help the mould life
quite
a bit.	If you have a plastic supplier anywhere nearby, you can check
and
see if they carry a spray-can type mould-release suitable for RTV. 
Though,
I've done a bunch of resin casting with my 2-minute setup stuff (great
for
hobby purposes - it's odourless, it mixes in a 50:50 ratio so it is
*easy*
to measure accurately, and you can demould in 2 minutes or less) and my
moulds are all ok without using mould-release at all.

Now, having rambled on about all that, if you *like* your dental plaster
and if it's good for the purpose... tell us about it!  Let us know how
it
goes.

>From: "Scott Clinton" <grumbling_grognard@hotmail.com>
>Subject: Re: [SGII] Modular Starship Terrain AND CASTING
>
>>...plaster actually labelled "Plaster of Paris" on the container is
>>what you want.  It is used for outdoor garden statues and
>>architectural mouldings, so it is quite strong.
>
>Hmmmm, I did not realize PoP was that strong.	I was intending on using

>dental plaster.  From what I have seen it is very strong and it is also

>cheaper than resin (and a lot easier on my molds).  I can get the
dental 
>plaster pretty cheap, but it is still a bit more than PoP.
>
>I have two masters done (both walls) and got my RTV...making progress. 
:-)

********************************************

Adrian Johnson