New Mold Prep and Fast, Easy Break-in

  • 1.7K Views
  • Last Post 27 January 2017
Ed Harris posted this 25 January 2017

New mold blocks usually have some residual residue of cutting fluid used in their machining as received. Getting good castings requires this residue be either burned or washed off.  Most people just start casting away after pre-heating the mold blocks, perhaps smoking the cavities to help matters along.  I used to do this too until I was taught a better way which seems virtually foolproof.

When I take new aluminum mold blocks from Accurate or NOE out of the box, I use a horsehair acid brush from Brownells to coat and lightly scrub the cavities and all surfaces of the mold blocks with Palmolive dishwashing detergent.  I then separate the mold block halves and place them cavities up on the bottom of a coffee can, rinse them lightly in hot water from the tap, as I fill the coffee can about half full, with more than adequate water to cover all surfaces and allow extra for boil off.

Bring the water up to a full rolling boil, then after 5 minutes turn the burner down to low heat, and maintain a slow simmer for at least 30 minutes. Afterwards remove the can from the stove, with pliers, place it in the sink and run hot tap water through it until all the suds and detergent are rinsed out.

Remove the rinsed blocks from the can, assemble them onto handles and pre-heat on your electric hot plate, using a 350 degree Tempilstik crayon to regulate the temperature while your lead pot heats up.  The detergent boil leaves the blocks chemically clean and a neutral gray color.  Once your lead melt is up to temperature, about 700 degs. F. and the Tempilstik mark has indicated the blocks are adequately pre-heated, you can cast good bullets immediately with no smoking.

73 de KE4SKY In Home Mix We Trust From the Home of Ed's Red in "Almost Heaven" West Virginia

Attached Files

Order By: Standard | Newest | Votes
R. Dupraz posted this 25 January 2017

I use basically the same process with aluminum molds. Only simplified a little. All I do is boil the new blocks in a SS bowl for about 30 minutes with a concentrated solution of liquid Dawn dish soap on the kitchen stove. Usually by this time the cavities have a uniform grey coating which is the key. Then rinse in hot tap water. Then plug my digital thermometer probe into the blocks, and heat them to 400-425 degrees or so while the pot is coming up to about 750.

I have used this method on new steel mold blocks as well, But what generally works for me with steel is a good lengthy scrub with brake cleaner. Unless the particular mold is balky then I have been known to boil and smoke them as well. That's why I keep some old  wooden farmers matches handy.

But I don't strike them on my overalls anymore. Never really could get the hang of that anyway.

Attached Files

Bob 11B50 posted this 26 January 2017

I boil the blocks, disassembled, in a pan dedicated to cleaning molds then rinse in hot water and then allow to cool.  I do this 3 times.  Then I heat in the oven at 450* for 30 minutes, then let cool at least an hour.  I heat the molds three times this way.  After the cleaning and heating operations have been completed, I then re assemble and check the handles and how the blocks align on them.  

After the blocks and handles are set up, I will cast after warming the blocks on a hot plate.  Usually the molds are casting acceptable bullets within 3-5 casts.  I cast 10 bullets that go ba ck into the pot, from there on most are keepers and get well checked.

 

Bob 11B50

Attached Files

  • Liked by
  • RicinYakima
JeffinNZ posted this 26 January 2017

Pretty much what I do Ed.  A tooth brush and dish wash liquid.

Cheers from New Zealand

Attached Files

David Reiss posted this 27 January 2017

Hey Jeff,

Down there do ya'll get double use from your toothbrushes, or use a dedicated one for mold cleaning and another for teeth cleaning? Just wondering, I like to be worldly that way.

 

David Reiss - NRA Life Member & PSC Range Member Retired Police Firearms Instructor/Armorer
-Services: Wars Fought, Uprisings Quelled, Bars Emptied, Revolutions Started, Tigers Tamed, Assassinations Plotted, Women Seduced, Governments Run, Gun Appraisals, Lost Treasure Found.
- Also deal in: Land, Banjos, Nails, Firearms, Manure, Fly Swatters, Used Cars, Whisky, Racing Forms, Rare Antiquities, Lead, Used Keyboard Keys, Good Dogs, Pith Helmets & Zulu Headdresses. .

Attached Files

Eutectic posted this 27 January 2017

For decades I have been taking off the sprue plate if possible and soaking for 20 minutes in clean mineral spirits, followed by a mineral spirits rinse and then a rinse with denatured alcohol. Assemble preheat etc. Most times the first bullets cast are good.

I store my molds in ammo cans with desiccant, so I never have to clean them again. Preheat and cast, then back in the can still warm.

Your method is more environment friendly, I may have to try it on my next mold.

Steve   

Attached Files

JeffinNZ posted this 27 January 2017

Hey Jeff,

Down there do ya'll get double use from your toothbrushes, or use a dedicated one for mold cleaning and another for teeth cleaning? Just wondering, I like to be worldly that way.

 

David, as frugal as I am I use an ex tooth brush for mould cleaning.  Like spent primers, expired bicycle tubes and out grown children's clothes there is never a shortage around here. 

Cheers from New Zealand

Attached Files

  • Liked by
  • delmarskid
Close