Mold Temperature

[Crummyshooter]

I'm sure this has been beaten around enough, but I'm going to ask anyway.
Casting with a brass, 2 hole, .375, 255 grain mold, timed at 30 seconds drop. Does the mold increase or decrease in temp? Either way It must reach a point where it doesn't change anymore. Just for a point of reference, starting mold temp is 400.

[Calamity Jake]

Lead temp and casting pace dictates mold temp, the faster you cast the hotter the mold will get.
You need to set a casting pace that keeps the mold at a temp that produces good boolits.

[higgins]

Lead temp and casting pace dictates mold temp, the faster you cast the hotter the mold will get.
You need to set a casting pace that keeps the mold at a temp that produces good boolits.

Yet casting slow enough that you don't smear lead across the underside of the sprue plate or across the top of the blocks. A few days ago I kept the correct pace for a long time and then got impatient with a couple of pours and made a mess of the underside of the sprue plate.

[runfiverun]

that's why many of us run the top of the mold with an oil like 2 stroke or anti-sieze or an A/C100 ester-oil.

[country gent]

If casting with a single mould I run the pace based on the sprues solidifying as a gage. I want the sprue to solidfy and "frost" over in 5-7 seconds. I llde cast and dont worry about a sprue but pour a ladle full oflead into the mould letting the excess run back into the pot. This keeps the spue hot and molten much longer as the bullet cools and solidifies. Sprues poured in this manner dont show the sunken surface like others do since the bullet has cooled and shrunk while the spure is still molten and forming. With brass moulds ( I cast with several 38cal 38 cal 365 grn 40cal 400grn and 45 cal 550 grn) I find running a little on the "hot" side isnt as big a problem as with aluminum or iron moulds. Another thing is brass moulds dont loose heat as fast so fluxing or short breaks you dont normally drop below operating ranges .

[John Boy]

Any material mold and any single or multi cavity mold:
* Bring the pot & mold temperature up to the degree so that a 5 second ladle pour frosts in 5 to 8 seconds
* Then mark your molds with that temperature & alloy for future reference

[warf73]

that's why many of us run the top of the mold with an oil like 2 stroke or anti-sieze or an A/C100 ester-oil.

This is what I do also, I've got a small bottle of 2stroke oil and Qtips behind the casting pot. Add a little bit once you see it start to smear(little goes along ways) and keep on casting.

[JSnover]

Does the mold increase or decrease in temp? Either way It must reach a point where it doesn't change anymore.
You could probably detect an increase as soon as you fill the cavities, continuing for a bit as the boolits cool, the mold absorbing heat from the cavity (it has to or the lead would never solidify, right?). The point where "it doesn't change anymore" is actually a point where the temperature fluctuates the least and is repeatable, which determines your cadence: The mold isn't getting so hot that you have to wait too long or so cold that you end up pouring a lot of rejects.

[gunarea]

Hey Crummyshooter
This particular issue has been, as you point out, ridden hard and put up wet. A while back I posted my solution on CBA. Rather than try to replicate the post and comments, I will give directions to the answer. The title of the thread is "Cooling the mould". In the bullet casting section, bullet casting sub-section, three or four posts from the bottom of page one. It comes complete with photos, ignorant criticism, accolades and a jealous challenge. If seriously interested in consistent temperature and increased cadence this is a must see article. Best of skill to you.
Roy

[OS OK]

that's why many of us run the top of the mold with an oil like 2 stroke or anti-sieze or an A/C100 ester-oil.

Using the Q-Tip to smear the top and bottom of the sprue plate and the cavities will make those casts jump out of the mold. I don't mean a heavy smear just ever so lightly and even and thin, very thin so that you don't even notice it there but it is...I use it on the pins and the sprue plate screw assembly, threads included.
Anti seize is made especially for high temperature and it lasts a long time, doesn't turn to a sticky mess, just performs flawlessly cast after cast.

[mold maker]

It's the time between opening the sprue/mold and the next pour that is the cooling factor. All the time spent with the sprue open on both sides to the air along with the time the open mold is fanned about. Control those and the cadence used can be stretched a bit. The lead temp can also be reduced a bit with good control of open time. As long as the mold is absorbing heat from the melt faster than it gives it up to the air, you are heating the mold. At the point, it gives up more heat than gained from the melt it is cooling.
The newby factor usually comes from inspecting the last boolits before refilling the cavities. This is air time where cooling is fastest.