Frosting in the middle

[abunaitoo]

I've got a group buy Lee 190gr 315di GC 6cav mould.
I was trying to cast tonight.
I smoked the mould.
Lead temp range from 500 to 800.
Mix of WW and range lead.
Flux with saw dust and stirred with a wooden cop stick.
Problem I'm having is the boolets seem to be over heating in the middle.
Very frosted. Sometimes so much that it's not filling out.
I started at 800 and went down to 500 in temp. Better as the temp went down, but started to wrinkle.
Any ideas????

[DLCTEX]

I cast some TL boolits this week end. I got the best relief from this problem by lowering the temp and pressure casting. Adding some tin helps also.

[BABore]

Check out the post on ugly frosted spots a few posts above this one.

Pressure pouring with a high flow rate is one way to overcome these frosted spots. It comes from mold overheating, usually at the thinner sections of the mold.

I use a ladle and pressure pour to avoid them. My alloy temp is typically around725-750 F. I dip my mold in the pot for 15-30 seconds to get it hot. Actually, it's too hot as it takes the sprue 20+ seconds to solidify. The first boolits dumped are extremely frosted and almost galvanized looking. But, they are perfectly filled out. I have a small, high speed fan clamped to my side table in which to cool the mold and sprue plate. Using the fan, it takes 2-3 casts to work back down to a more normal mold temperature. For most of my molds, I look for the sprue to set up in 3-4 seconds without fan cooling. I pour a real healthy sprue that usually covers most of the plate. This is good as it allows the boolit bases to slowly suck in enough alloy to completely fill out. After the sprue solidifies and shows the color change, it is held in front of the fan for 3-4 seconds then cut. The sprue goes right back into the pot. I don't get all anal about not tearing the base slightly. No gaping craters are allowed, but some slight tearing is just fine. If you strive to get a perfectly shiny, clean cut, sprue you are likely to run into more unseen air pockets, poor fillout, and more weight variance. It goes against common casting wisdom, but it works. Keeping the mold temperature up and more consistent produces better boolits than making the sprue look text-book perfect. Accuracy tests also bear this out. Consistency is the name of the game.

After the mold is emptied, it is held open in front of the fan for a timed count. How long depends on the mold. Usually it's less than 4 seconds. Once you get into a good cadence, watch the sprue freeze time to adjust your fan time. As long as you can keep the mold at a consistent temperature that produces good boolits, alloy temperature can be ran quite low.

[Echo]

And could be the mold still has some oil/whatever in a location causing the non-fill and frosting. Or a problem with venting...

[abunaitoo]

Thanks
I cleaned it with hot water and soap using a tooth brush.
I then dried it with a propane torch and smoked it with a butane lighter.
I do the same for all my other moulds and have no problems.
I remember the first time I cast with this mould it wasn't this bad.
Boolets came out kind of shiney, but not frosty. Sharp corners. No pits.
I don't have any tin to add, so I'll try pouring slower, faster and pressure to see if it helps. Also try to jack up the temp to try and get all frosted, then lower to see if I can get the shinny. Don't really care if their shinny or frosted, but I want good fill out.
I'll try again tonight.

[montana_charlie]

You say your alloy is w/w and range lead.
Range lead (if I read correctly) is considered to be pure lead.
Mixing the two brings the small percentage of tin (in the w/w) down close to 'nuthin'.

To get good fillout with an alloy that has 'nuthin' for tin will take a lot of heat.
CM

[Wayne Smith]

Charlie, I think range lead usually has 2-3% antimony in it - .22's do and many condom bullets do.

[abunaitoo]

I tried it again.
Same thing was happening.
I got out another Lee custom 6 cav to compare.
The vent grooves were not as deep on the problem mould.
I used a tooth brush and cleaned off the soot from the surface, leaving the boolet cavity untouched.
Problem solved.
I'm thinking the soot was blocking the vent grooves.
Works great now.
Just finished casting about 300+ boolets.
Thanks for all the suggestions.