Metal Casting Zone

Please forgive the basic question, I'm new to hot molten metals.

Everything I've seen on the boat building forums says keep Hot Molten Lead away from Water. The water flashes and the lead splatters. None of this is a good thing. There's talk of how long to heat a mold in the oven for to bake off the water etc.

Yet I see Green Sand, ie Slightly Damp Sand mixed with a particular type of clay used as a mold for metal casting.

My understanding is that

1) There's not a lot of water in the sand.
2) The sand is porous, so the steam can escape.

Am I missing something.

I need to make a lead shoe for a center board. A sink weight. About 5kg of lead.

I can cut a square in the Centerboard and pour in the lead, but a nicer solution is to make a mold from the bottom of the Centerboard, pour the lead in, and when it sets, cut the right sized bit of the bottom of the Centerboard and bolt on the lead shoe.

I can use bronze pins at different angles for the shoe, so it will NOT fall off.

Making the mold is the confusing bit.

Hi rationalroot ,

I don't think you're missing much, keep molten metal and liquid water apart! Green sand is damp but only just so, when molten metal ( even white hot iron ) hits it the water near the metal vaporizes but there is so litle of it that it pases through the pores in the sand. Borrow a book on metal casting from the liburary, one of them should explain enough for you to cast a bit of lead.

Good luck.

Peter.

www.metalcastingzone.com/metal-casting-forum/lead-casting/8-tons-casting-lead

Yours isn't as large as this guys. His seemed to work out well. He used a concrete mold and poured the whole keel. 8 Tons!! What am I talking about, he made the whole boat from start to finish. Check out his blog in the thread.

I don't know how lead will do in green sand. Should work but may be a rough surface.
Let us know how it goes.

when I had to cast some weights for a long case [grandfather] clock a couple of years ago I toyed with using my greensand, in the end I used co2 sand & both weights came out well,no spluttering & a perfect finish.

I assume you were using Sodium-silicate/waterglass, and were you able to use the molds more than once? I may have to try some.

Welcome to the forum.

I hate sputtering!!

hi jammer, yes it was sodium silicate or waterglass [my dad told me they used to preserve eggs with it during the war!!!] they were cylindrical about 2" in diameter with a steel hook cast in to hang them from the pulleys I used tubing for the patterns & put the steel hooks in from below,I melted the lead & poured it in then I played a sievert blowtorch on the top so it wouldn't leave a shrinkage depression [cast vertically open top] which was actually the bottom, I ''scrounged'' the sand ready mixed from a local jobbing foundry & put it in a plastic bag to take it home,I was wary of using greensand because of the water content,I suppose I could of used petrobond just as well, I had to break the molds to get them out so couldn't re-use again.