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I have just finished casting a couple of sleeves (liners? collars?) to protect the front opening and the rear pass-through port of a gas forge that I’m building. I opted to use Kast-O-Lite 30 LI, which should provide durability and some insulating value. This is the first time I’ve used this product (and the first time I’ve built a gas forge), so this is basically just part of an experiment, and NOT a recommendation for anyone else, although I hope it is of some interest to the community. I'm open to suggestions, since none of these ideas are "cast in concrete," so to speak. I realize that there are easier and faster ways to protect the forge openings, but I’m not in a hurry, and I enjoy the design, fabrication, and experimentation aspects of my various projects. As long as I’m having fun and learning something, I don’t mind extra work. I'm building this forge as an "experimentation platform" to try out different insulating materials, burners, and other features, so I'm building it so that the front and back (the modified end-bells of an old tank) are both easily removeable. More about the forge itself later in another post. For now, this is just about the abovementioned sleeves. For the rear pass-through port sleeve mold, I cobbled together some scrap wood, coated the inside with several coats of carnauba wax mold release (buffed a bit after each application), and for a sacrificial core I shaped a piece of XPS (extruded polystyrene) insulation, which I coated with silicone rubber. I didn’t want any taper in the passage through the sleeve, and the XPS was easily dug out after the refractory had set. For the other mold, I used the front of the forge (the front end-bell of the old tank) for part of the mold, supplemented by three pieces of silicone-coated XPS and a doubled cardboard tube (Quik-Tube) temporarily adhered to the inside of the end-bell. I allowed for a little expansion room between the castings and the steel openings of the forge. I also put a radius on all inside corners of the castings to help reduce stress risers. After the castings were removed from the molds, I radiused the edges that would be directly exposed to hot exhaust gases and high radiated heat (I might increase the radius on some of those edges later on). All other sharp edges were eased a bit. A diamond file worked very nicely for the "fine-tuning" work. I’ve seen various types of “stainless-steel fibers” for castable reinforcement, such as needles, melt-extract fibers, hooked-end fibers, wavy fibers, etc., with needles being the type I’ve seen mentioned most often. However, instead of buying ready-made stainless fibers, I experimented with some DIY stainless fibers...about 2% in the mix. I don’t know if that’s an appropriate percentage for the fibers that I made, and don’t ask what the fibers look like...just yet, anyway. After I’ve used the forge for a while I’ll report on the success or failure of the castings and fess up about the DIY fibers I used. For now, suffice it to say that I used somewhat different fiber shapes for each of the castings. Frankly, in retrospect, I probably would have just purchased some off-the-shelf stainless fibers. I tried to come close to the manufacturer’s recommendations for mix-to-water proportions, and I tapped and vibrated the molds to the extent that I thought was appropriate, based only on intuition. If I had more experience with this castable product, I might have more specific recommendations. By the way, in anticipation of some questions, I’ve come up with a few workable approaches for supporting the sleeves in the end bells on all three axes while maintaining good insulation values and allowing for expansion/contraction, but I haven’t settled on one yet. I’ll post pictures when I do. It will probably involve the use of some ceramic insulating board, but that's about all I can say right now. Next, I’m going to try to match the recommended dry-out schedule for the castings as closely as I can. I've also thought about applying a coating of ITC-100 to the castings after they are fully cured and have been through a few firings of the forge, but I want to research that possibility before applying the coating. Has anyone here used ITC-100 or equivalent directly on a castable refractory, and what are your thoughts? Mold for the rear pass-through port sleeve: Pass-through port mold after screeding (I didn't trowel the surface): Mold for the front entry sleeve: Mold for the front entry sleeve after screeding: The castings: Inside view of the front end-bell (made by welding a perimeter flange and a flat front plate on the end-bell of an old tank...and wearing out a few sanding discs). The openings in both end-bells are actually centered; the camera angle just makes them look offset. Inside of rear end-bell (made by welding a perimeter flange and a square tube on the other end-bell of the tank): Front entry sleeve as it will appear in the end-bell: Inside view of front entry sleeve: Rear pass-through sleeve as it will appear in the end-bell (I may shorten the sleeve about 3/4 inch): Inside view of rear pass-through port sleeve: Comments, questions, and suggestions are welcome!