Breaking in a new mould

[35Whelen]

Good day to all you veteran boolit casters.

I am new and just getting all my equipment to begin casting. Luckily I have a tire shop here in town that donates a couple five gallon pails of WW every time I bring in a case of beer, so I now have a lifetime of lead.

I have been getting my moulds bought and paid for from both Mihec and Accurate as well as NOE.

My question is this: Once I clean the mould in hot soapy water I know I should break the mould in by placing it into a 400 degree oven for an hour and then cool it, repeating the process 3-4 times.

Firstly will this apply to both the brass and the aluminum moulds?

Should I wire the mold halves together will in the oven to keep them aligned as they heat up and cool down?

Thanks and best regards
Paul

[plainsman456]

I just cast a few times getting the mold up to temp,then let it cool.

I usually do this 3 or 4 times,then go for it.
Using 2 molds while waiting for it to cool helps with the down time.
I have also placed the hot mold on a steel plate to help draw out the heat,kinda speeds up the process some.

[geargnasher]

Heat cycling NOE's moulds per Swede's instructions is a good idea, he isn't kidding about heat setting the pins. If you do the same with brass moulds, it helps build a patina on the surface of the cavities that resists lead sticking, so it helps to cycle them a few times prior to casting.

However, I skipped the heat cycle with the last brass mould I got and smoked the cavities with a butane bbq lighter instead. Normally I absolutely abhor the concept of smoking a mould, but it does help the break-in without getting any lead buildup on the cavity edges. After casting, I dusted the soot off the mould blocks with a shaving brush and put it away to use the next day, at which time the mould only required a faint smear of ester oil on the sprue plate to run another 20 lbs of boolits.

I still learn something new every time I cast.

Gear

[RobS]

I put my molds on the handles and then put the mold on my hot plate and turn things on like I was going to cast. Once the hotplate and mold are up to temp I shut down the hotplate and leave the mold on top for everything to cool down slowly. Do this another time and then the third time heat things up and start casting.

I also clean all my molds with Dawn dish soap and hot water prior to work the heat cycles.

[btroj]

I find that aluminum moulds can benefit from a cleaning, heat cycle, and clean again. The second cleaning seems to remove oils that the heat cycling brought to the surface.

[capt.hollis]

Would you have to do this to a new Aluminum mold too ?

[RobS]

Would you have to do this to a new Aluminum mold too ?

When I first started out I didn't heat cycle my first molds (Lee molds). Now a days I typically have custom molds cut so I take a bit more time and work them into the heat cycles and then cast. I don't know if I need to do this with the aluminum molds or not I just do with all of them.

[Boolseye]

I do follow Swede's instructions for breaking in a NOE mold. I stand my NOEs on end on a hotplate, handles in the air. Heat it up to 3-400º (15 minutes or so), let it cool to room temp, do it a couple more times, when I'm around the house doing other chores, not as a special event.

[Mal Paso]

Heat cycle with the blocks open and cavities exposed to air for the most benefit.

Cool slowly.

[Oreo]

After learning to heat cycle my brass Miha molds I'm thoroughly convinced of the importance of slow even heating and cooling. Not so slow that it takes a long time but slow enough that the block heats evenly. My theory is that uneven heating of the blocks is what warps them, not the temperature itself.

[35Whelen]

Thanks Guys....really appreciate the insight of each of your methods. Makes sense.