Mold pre-heat guidelines

[Engieman]

Going to start preheating my molds before casting. I have always cast and re melted the wrinkled bullets until I got up to the proper temperature. Sounds like I can get up to speed quicker by preheating. Got a new electric range top with a solid top....not bare coils. Looking for any guidelines or advice in this regard. Have both brass and iron molds, don't want get too hot and damage the mold. Sprue side down, warm setting, any temp guidelines?

Advice and recommendations appreciated, thanks

[Strtspdlx]

I turn mine on when the pot goes on, I usually run almost at the highest setting, when the pot is ready so are my molds. you may have to play with it and see what you prefer, I did notice my first pour my mold is always too hot, but I'm okay with that because after a handful of pours the heat evens out throughout the mold and it doesn't take much time to cast good bullets.

[OS OK]

I can't remember exactly, seems like I measured 360 to almost 400*F. I used a digital hand held laser type pointer thermometer and it reads differently from one shiny surface to another...actually I think it's more of a 'ballpark' guesstimate rather than exact.

This I do know...on my 1,200 watt hotplate with a skill saw blade over the coil, I have the temp. knob set at 50%, 1/2 way up to max.
If I start warming the mold when I start the 20 lb. pot, they are both ready at the same time and...more times than not the mold throws good boolits from the first pour.

Pre-warming the mold this way is the best advice I ever got, trying to balance a mold partially submerged in the Pb on the edge of a pot was risky business for me...almost let one slip off to the floor.

[Loudy13]

I started doing this with what sounds like the same hotplate that you have. I put it on medium and take the temp with the ray gun from time to time with the plate at about 350-400 it heats the molds enough that a couple casts and its good to go. Probably the best addition to the set up.

[country gent]

Ussually in the 300* - 400* range is a good starting point for most moulds. It may take a little experimenting with temp, time and such to find the magic spot. Also remember some materials disperse heat differently. Aluminum will heat thru quicker but also radiate more away. Steel will warm closer to the heat source much quicker than at the top. Brass will heat fairly evenly and hold heat longer. I also cover moulds when pre heating them to keep air currents from pulling heat away.

[toallmy]

I would like to thank Bangerjim for posting preheat the mold so often I finally started doing it . If I use the kitchen electric stove with a steal plate on the burner at medium on aluminum or steal molds is about right but my little hot plate in the basement needs almost 3/4 to get good and hot . It truly made casting so much smother , I would in the past have good days or bad days casting now they are almost all good days . 20 minutes usually gets it hot enough to get started .

[Bodean98]

An added bonus to using a hot plate.
If in the middle of your casting session you need to stop casting(need a drink, answer the phone, take a pee) you can fill the mold and let it harden, cut the sprue and put it on/in the hot plate. When you return you dump the boolits and resume casting as if you never stopped!
A hot plate is a great addition to your casting setup.

[bullseye67]

Good evening, I have been using a hot plate to pre-heat the mold for years. The first one I had finally burned out a couple years ago. It was from the 70's, came to me as a hand me down from a family member. Makes for perfect boolits from the first pour. The other reason to have a hot plate is for pre-heating ingots before adding to the pot. In the winter the condensation from cold ingots "can" bring a visit from the tinsel fairy. I got into the habit of having a stack of ingots pre-heated year round. The pot stays at operating temperature as the ingots are added, no waiting, just keep casting. Just make sure you use gloves or pliers to add pre-heated ingots to the pot.

[Outpost75]

I have a small single burner Proctor-Silex hotplate from Walmart next to the casting pot. I cover the Calrod with a piece of ceramic tile to rest the mold blocks on. I use a Tempilstik 350 deg. F indicator marker on the mold block to calibrate the hotplate temperature. The hotplate setting on the dial may vary depending upon ambient temperature in the casting area, I cast outdoors on a screened porch to ensure adequate ventilation. During spring and summer a Medium setting on the hotplate is about right, in winter when it is below freezing I crank up the control between Medium and High, but the Tempilstik crayon is the Bible.

I condition new aluminum mold blocks by scrubbing the cavities and all exterior surfaces with Palmolive dishwashing detergent, using a soft horsehair paintbrush, then I separate the blocks and place them cavities up in the bottom of a coffee can, filled about halfway with hot tap water, bring to a full rolling boil, then turn down the heat and simmer them for 30 minutes. Then take the hot can, holding with pliers, into the kitchen sink and rinse thoroughly in hot tap water until all the suds are washed away, then assemble the blocks onto handles and warm on the hot plate. New aluminum blocks so treated do not need to be smoked, but will have a uniform gray color, and with the 350 deg. F. preheat, you should get good bullets immediately.

Once the mold has been conditioned, this doesn't need to be repeated, just preheat and cast away.

186857

[longbow]

My rule of thumb for pre-heating moulds is to pre-heat until the sprue plate lube just starts to smoke. That is actually slightly hot so the first few pours take a few seconds for the sprue to harden then I settle into a rhythm for casting steady.

It works for me.

Longbow

[rototerrier]

I have one of those cheap HF hot plates and over time I was able to determine setting the dial on the last M in mediuM gets my molds right where they need to be. If It's a bigger mold, sometimes I come up to the D. If I go past that, the first pour takes a while to solidify. Not really much to it other than that. Easy and simple.

[oger]

I use an old toaster oven set a 400 deg it gets the molds close enough to start.

[sw Idaho]

With preheating molds, what temperature do you keep you lead at?

[CHeatermk3]

That will depend on the mold--Material, size of boolit, number of cavities, alloy will all affect this.

Best thing is with a new to you mold, experiment till you find what works for a particular mold/alloy and keep a note as to the temp of the alloy that produced good boolits.

I'm still struggling with some of my molds to hit the right combination!

[gwpercle]

I don't like getting water into my moulds , I clean mine with disc brake cleaner or acetone and an old tooth brush. Letting them soak for an hour pulls out all the machining oils.
Gary