Making More Bronze (Session 7)
(cracked mold with a drop of bronze inside) For our first session this year (the weather has not been cooperative), our plan was to make more bronze because we're almost out and we have lots of plaster molds (made over the winter) to fill. So we loaded the crucible with copper and tin, 90:10. in the hope of making bronze to cast it in our patiently-waiting molds. (NB: I realized later, though, that our 90:10 calculation wasn't quite right. We measured the 10% tin in relation to the amount of copper we had, but I think it should be in relation to the final amount of bronze we'll end up with. So we may in fact have been short about 6-7 grams of tin for a true 90-10 ratio. Would that be significant? Would it have helped bring the liquidus temperature lower?) Many of the molds were cracked, as you can see. It was more than likely that they got too hot too quickly in the kiln, during the wax burnout earlier this year. (The sprues are covered or stuffed to keep them clean before...