20 gauge slug mold help

[seawolf]

I bought a used Lyman 20 gauge slug mold and I have cast about 200 slugs with it. today I was casting again and got called away to help the other half. when I came back I placed the mold on the rim of the remelt pot to preheat as I usually do it cast the first 5 or 6 fine then I started getting a void in one side of the slug each time I cast.
I have looked in the mold and see nothing to cause this.
I have added some tin solder to the remelt pot and wax fluxed twice.
I am letting the mold cool now so I can take it off the handles to inspect it better.
should I polish the inside with steel wool then re- smoke the mold or is there a better way to do this?
Mark

[bhn22]

Is it a frosted, indented area, about 1/2 way down the slug? If so the mould simply may have overheated a bit, which on these bigger cavities sometimes shows up as an imperfection in the area of the mould handle cutout in the outer block. Another possibility could be from ladle casting if you're casting that way. If you rotate the blocks as you pour, your stream could be hitting the exact same spot time after time. If the moulds pretty thin in that area, it could overheat that way and cause an imperfection. This could go hand in hand with the first scenario. With their thin skirts, foster type slugs can do interesting things at times. I've traced both of these conditions down as likely causes for issues in my slug casting days, so I'm not just sitting behind the computer hallucinating, as some seem wont to do.

[Blammer]

yep, let cool start over should have no problems. Don't monkey with it until you try casting again with it in another casting session.

[seawolf]

I am using a Lyman bottom spout pot that I bought used so long ago I think it came over on the mayflower. I hve been reading of others problems but I had not heard that one. I will still take the mold apart and clean the vents with a copper wire as I read in another post also.
thanks, Mark

[seawolf]

I think I have bugs out now. old Lyman mayflower pot died last night so I bought a lee 4-20 and thermometer this morning. pot set at725 and casting is good now.
Mark