From: Scott Clinton <grumbling_grognard@h...>
Date: Sun, 28 Oct 2001 23:43:00 -0600
Subject: [SGII] Modular Starship Terrain AND CASTING (OT?)
Howdy All, I have been doing a bit of mold making and casting of 25mm modular starshp terrain I just wanted to relate my experiences to those who care. Firstly, RTV Silicone is great! I will never use latex for mold making again for this type of thing. I used Polytek PlatSil 71-20 and it worked like a charm I also tried Polytek PlatSil 70-25 and although it worked it is not nearly as good as the other. I just had to be careful of a few things (as warned by others) like not whipping air into the silicone when mixing. I had to paint the details before pouring and you have to pour sloooowly. The most important thing as I can see is to have the entire process planned out so that you are able to start and finish "the pour" without any hesitation while still not having to rush. I had no big problems on my first 3 molds and I have been able to eliminate almost all air bubbles now (a vibrating table is on my Christmas list <g>). My evaluation of the dental cement I used in casting though, is less glowing (Pemaco Ortho-Stone). It works well enough, but it is pretty thick stuff when mixed according to the box. And when I have diluted it so that it will flow well into the molds, I fear it is no stronger than hydrocal or perhaps even reinforced plaster of paris. My biggest letdown is that I don't think I will be able to use this dental cement at all for the small, two part molds I have planned. It is just too thick (they are about 1/8" x 6" x 3"). But, I can still use it on some of the open face molds I have made and will make. It does mix very, very well and it has other advantages. I then tried some Alumilite (resin) I picked up from the local hobby store. This stuff works much, much better. But, I think if I shop around I can find a resin that is an even better match for what I want to do. Alumilite seems to exhibit too much shrinkage for what I am casting, and it has such a short pot-life that it can be tough to pour it fast enough. I am investigating a resin "RP40" by Thermocast. I have uploaded images of the first few resin pieces I have done. One is a wall and a door (they are actually cast separately) and the second is a floor hatch. I think I will end up casting all the floor hatches in dental cement though as I still have about 24.5 lbs. of the stuff to use up. :-( (if Hotmail mutilates these links you may have to cut-n-paste) http://home.swbell.net/grog1/casting_images/first_wall_and_door.jpg http://home.swbell.net/grog1/casting_images/first_hatch.jpg Lastly, if this is too off-topic somebody just say so and I will shut up about it, but frankly I am having a blast with this casting stuff. I highly recommend it to anyone that enjoys modeling. Later,