I saw some folks wondering about the possibility of using silicone molds to create EPS patterns in an older thread. I'm not sure if anyone ever tried it but I've been playing around with the process this last week so I thought I'd share my findings so far. My ultimate goal is to cast a brass ball-peen hammer using lost foam casting and it quickly became apparent that with my limited tools and skill set, sculpting a decent foam model wasn't going to be possible. My research into alternative methods led me pretty quickly to EPS beads. There are some good tutorials on Youtube for using EPS beads to make duck decoys. Finding a non-industrial source of pre-expanded beads was a little trickier but there is a guy on Ebay who sells them at a good price for making fishing jigs. The beads are smaller than those used for decoys but seem to be working okay. We'll see if the density is an issue. Following the advice of decoy makers, I coated the mold with oil and sprinkled in a layer of un-expanded beads to create a smooth outer shell. I pre-expanded the rest of beads halfway as needed in a measuring cup placed inside a pot of boiling water with a steaming rack in the bottom. (Not sure what this little stainless steel rack is called -- I stole it out of my wife's Instapot. It just serves to keep the measuring cup and later the mold off the bottom of the pots.) My first thought was to make a hollow core form around the temporary wooden handle I used when making the mold: This proved to be a failure as the steam had no way of penetrating the mold. I figured it would be easy enough to drill out the eye for the handle after casting so all of my future experiments did away with the wooden core. The form handle ends (see below) will probably give me a good place to attach gates, risers or vents. After the mold is prepared, into the pot it goes for steaming. My pot has a glass lid with a little vent hole for excessive stream. How long to steam for? Decoy makers with their aluminum molds do 60 minutes. After my failed first attempt where the steam didn't penetrate the silicone mold I've been going for an almost certainly excessive 2 hours after which I let it cool down before removing from the mold. Once I have a handful of decent patterns I'll play around with steaming time to dial this in a bit. For my second attempt I braced the mold top and bottom to keep it closed as the beads expanded but I ended up with lateral distortion as the beads pushed to the side. Still, the end result was very promising. Addressing this distortion seems to be the primary challenge in using silicone molds for EPS. The screen was to keep beads from leaking or expanding of of the hole in the mold. For subsequent attempts I moved it to the end of the hole. \ The picture above shows distortion in the direction I did not brace on that first successful attempt. My subsequent attempts having gotten progressively better as I've played around with clamping pressure and bead density. My fifth and six attempts show very little distortion, mostly at the face of the hammer. I'm not sure if this is because I'm still using too many beads or if it's because this is the one direction I haven't braced yet. I'll continue experimenting and let folks know what I find. Here are my first four successful attempts. Lateral expansion is getting better with each try but the face distortion is getting worse: Here are two views of my sixth attempt: That last one is probably close enough to get the job done. I can clean up the issues post casting. That said, I'm going to keep playing around with additional braces and fewer beads. Ultimately I think the process shows potential for complex shapes that don't require tight tolerances and can be cleaned up post casting. A welded metal box around the mold would minimize distortion but is beyond my resources currently. We'll see how the density works come casting time. I'm very interested in getting advice from folks regarding orientation and placement of sprue, vents and riser for casting. I'm new to the forums - I assume a separate thread in the lost foam forum be the best place for that?