Running a mold too hot?

[Archey]

It is well known that a lot of the common cast boolit quality problems, (wrinkles, poor fill out, boolits sticking in mold, etc.) can be eliminated by increasing the temperature of the alloy and in turn the mold. My question is then, why not just run the casting pot on high? What are the negative effects of an alloy / mold that is hotter than normal? When I first started casting, I tended to keep the alloy and mold on the lower side of the temp range and my quality struggled. I now cast with a lot hotter mold and alloy and my boolits are much better and casting is more enjoyable. I no longer have to beat my sprue plates open or tap the mold to get the boolits to drop. The only negative effect that I have experienced with hotter molds is frosted boolits but that is purely cosmetic from what I have experienced. What say you?

[s mac]

In my experiance if the melt is too hot lightly frosted goes to heavily frosted, rough texture, unusable, also your alloy oxidizes quicker with what I think is a loss of tin. Lets hear from the experts.

[montana_charlie]

The only negative effect that I have experienced with hotter molds is frosted boolits but that is purely cosmetic from what I have experienced. What say you?
Have you not measured a reduction in bullet diameter?
Are driving band and base corners not rounded?

CM

[JonB_in_Glencoe]

when running things hotter, I tend to see "shrinkage", especially in longer or heavier boolits and higher tin content seems to add to that also.
http://castboolits.gunloads.com/showthread.php?187202-March-2013-Photo-Submission-*Topic-Cast-Boolit-Imperfections&p=2102761&viewfull=1#post2102761

[osteodoc08]

Everything has an operating range. If your out of that range, you get poor quality.

My steps are as follows:

Clean the mold.
Preheat the mold while the melt gets up to temp. I cast 650-750 depending on mold.
Start casting and look at the quality and adjust parameters based on what I see.
I tend to find a good rhythm with 2 molds and will mold up to when the mold will start to frost and I let it cool while I use the other. I can go back and forth at a good pace.

You want to keep the melt from getting too hot as it will oxidize and you'll start to lose tin to oxidation and it will also hear up your molds too fast causing poor bullets.

Get a good melting pot thermometer and determine what works best for you. I keep mine marked with a sharpie where I like my melt temps. Also keep notes.

Generally my aluminum mold like to be run cooler. Iron molds like to be run hotter and brass in between. If I had to absolutely choose one material for molds, I'd probably pick brass. It doesn't rust like steel and has a wider temp "operating range" compared to aluminum, at least in my experience. That being said ill use any quality mold of any material. I still love my old iron Lyman's and aluminum NOE and Accurate molds.

[454PB]

The only problem with running the alloy temperature too high is that it accelerates oxidation and drossing.

What you need to control is mould temperature, and if you're running a high alloy temperature, it's easy to control mould temperature by keeping a wet cloth or sponge nearby. If you're mould gets too hot, just touch the bottom of the FILLED mould to the cloth. It doesn't take much, 2 or 3 seconds will cool it a lot.

[fattires]

In my brief experience I have found that when I cast too hot it takes longer for my sprue to harden enough and I end up with ripped sprues rather than nice cuts.

[hotbrew]

I've found that when the mold is just at the frosting point you get sharp definition and fill out. Keep going beyond that point and quality goes down. Once you are at the 'sweet spot', drop your melt temp a touch and pace yourself or switch back and forth between molds to keep bullets good looking and at weight.

hotbrew