Hi all, I'm conscious this is a very noob question and I'm almost embarrassed to ask it but I'm hoping you guys will appreciate I'm still learning this craft and won't take the piss too much! I had a little play over the weekend and poured some very simple moulds in brass with varying degrees of success. The patterns were various small trinket type thingies including a couple of key fobs. I had a central sprue which I gated off in a radial fashion to each of the items. I used Mansbond oil sand. Some of the items formed reasonably well but others refused to fill completely. I attempted this one a second time and while it did a little better it was still incomplete. Second time around I gated onto the back of the mould rather than onto the bottom edge so that the molten brass could run into it unimpeded. The pattern itself is approx. 60mm x 20mm x 3mm. I didn't use a riser because I didn't think it would be necessary for something this small - am I correct in thinking risers become more critical the larger and more complex the piece is? I also didn't use vents but would that alone give rise the failure seen here? As an aside, I have learnt that molten brass gives off Zinc Oxide fumes which aren't great for the health. My workshop/garage is well ventilated - garage doors wide open plus a side door, so plenty of through draught - but do you reckon I need to take more precautions? Many thanks in advance. P.S. - SomaFM is an awesome Internet Radio station ... check it out!!