#DIY #video about molding gray and brown concrete in silicone molds to make trays and cups and stuff. Suggests using a hammer drill on the non-rotating setting, or a Theragun vibrator, to vibrate air out of the molds after setting them on top of a wooden board. He likes cutting lids for the concrete things out of hardwoods. No thoughts on concrete reinforcing fillers or foaming. He suggests using a box cutter or screwdriver to trim flash or sharp corners, or a sander or angle grinder, or just rubbing the edges of the (presumably mostly uncured) concrete against a block of wood because it “breaks off all the little crumbly pieces”. He also suggests curing the pieces underwater, ideally in distilled water. Finally he applies some kind of “sealant or curing finish” after letting the cured concrete dry for a week, preferring a few layers of Home Depot cutting board mineral oil. In one case he tried coating the bottom with TotalBoat epoxy resin with black pigment, setting the pieces face down on a silicone mat to cure, trimming the epoxy overflow with an X-Acto knife perhaps a bit later than he should have, or in one case a wood router with a flush-trim bit. For making silicone molds, he recommends Smooth-On Mold Star 30 around forms made of legos
#Steve-Mould #video on counterflow heat exchangers; he built a tube-in-tube one using a clear outer hose and a copper inner pipe with a spiral of copper wire around it as a spacer. Mentions counterflow washing used in mining, which is a sort of semi-batch process with a series of washing tanks, which I hadn’t heard of before, with solids being progressively moved to cleaner and cleaner tanks in the cascade.
#PDF of the #documentation for the #SPL systems programming language for #HP’s #HP-3000 line, which looks pretty similar to C and Pascal. #retrocomputing