Cloud chamber not working

So I made a cloud chamber. I'm using 99.9% isopropyl alcohol, And a lot of it soaked into cotton wool at the top of a fish tank. That's on top of a metal plate painted black with socks filled with dry ice from fire extinguishers (can't buy dry ice easily in the UK).

I leave it for 10 mins or so I get droplets falling but no trails. I've even added uranium glass and a thorium gas lamp filament in there and still see no trails just droplets falling. Can move a torch round and see those drops easy but absolutely no position gives me any trails.

Any ideas what my issue is? Can you over saturate the alcohol? It soaks up a hell of a lot of it when I pour it in on dry cotton wool.

Yes that is an iron/nickel meteorite holding it down

I had the same problem, until I put much more dry ice and the plate must directly touch the ice (really push on it) as much as possible. Also too much isopropyl alcohol can over saturate the chamber so be careful that the droplets are not too big (more like a really fine mist above the plate). Then shine a strong light from the side.