Sand Casting Aluminum ashtray / bowl

This is a casting I made of a glass ashtray (pattern). In this post I refer to it as a bowl because I am not a smoker. The only small problem was that the inside part of the glass bowl was curved in, so if I would sand mould the glass bowl the way it is the sand mould would break while lifting the cope part, so my solution was to use filler inside the ashtray and smooth the curve the other direction. After the filler was dry I used fine grade sand paper and two coats of clear varnish over it to prevent the sand from sticking. Using glass as a pattern is great because it is very easy to remove it from the sand and the finishing is superb quality. The only thing is while ramming it have to be careful not to break the glass with the rammer.

Here is another small tip: As I've mentioned before always preheat your ingot tray and foundry tools that come into contact with the molten aluminum. Another thing that won't do any harm is to preheat the aluminum scarp or ingots before adding them into the crucible. Molten aluminum is 660C° and higher. Two things can happen if parts are not preheated , one is the safety aspect regarding molten metal splashing out of the crucible and the other is thermal shock or "aluminum freeze". The aluminum in the crucible just turns rock hard and back into a molten state after a few minutes.

The aluminum bowl turned out very well now I just have to think of where to put it : -)