Polished or Dull?

[Chris C]

I'm pretty darned new to casting, so I've an uninformed question!

Do you prefer your mold cavities polished or dull?.............and why?

Edit: This is an aluminum mold. Polished or dull?

[John Boy]

Chris, there was a study done by a BPCR gun crank ... remove cavity bluing with bluing remover - rinse in hot water - repeat 2x more times. The surface of a cast bullet is more smooth than a mold with bluing in the cavity

[Walter Laich]

I take a new mold, spray it with some degreasing stuff (though some will tell you this isn't necessary) heat it up and go to casting. Sometimes the Lee's will take 3-4 sessions to start dropping good bullets, Lyman and the others seem to be good from the get go.
Adding a bit more heat, within reason, when the mold is new seems to help.

[Connelly47]

I've found a shiny mold that has been smoked black with a beeswax candle will make good bullets in the first casting. Mold temperature has more to do with getting good bullets than any coatings.

[country gent]

Bluing causes a oxidation on steel that may affect castings finish some. I normally clean with a solvent dregreaser ( maybe even a short soaking in it). I dispose of this as adding back to bottle contaminates the whole bottle with whatever is removed from the parts. I then scrup good with dish soap water and a tooth brush really working up a foam, I do this twice. I then heat over low heat to speed drying. I then lube hinge points sprue plate and alighnment pins. Pre heat and cast. I did clean one set of steel blocks with dawn and lemishine it removed the bluing eerywhere it touched. After a couple sessions the were again a dark blkue with no reall diffrence in bullets size finish or consistancy. As long as the cavities are smooth without chatter or feed lines bullets should be good. If bullets need it I lap the mould lightly. Sticking bullets, slightly small size, machine marks or chatter showing thru ect ect. Normally a light lapping with flitz or simichrome maybe diamond lapping compound for feed lines or chatter. You just need to polish the surface not really remove metal unless its a size issue. The bluing induced oxidation on the surface may aid with bullet release as lead tin dosnt adhere as well to the oxidation.

[runfiverun]

I like the blued because it does help release the boolit it also protects the metal from brown rust forming.

[bangerjim]

I have LOTS of Al and Brass molds. Also several ferrous molds that are NOT blued. Bluing is only a chemical cosmetic surface finish that gives steel a nice look. It does not protect against rust.......unless you treat it with oil. Fresh blued steel will, in fact, rust faster than shiny steel. I use bluing on all the speciality machine tools I make, but ALWAYS rub them with light oil immediately to prevent surface rusting, even here in the desert!

My ferrous molds just do not rust.

Bluing could potentially increase surface grab (since there is no oil) and might lead to not-to-good release. But that is getting down to the microscopic level! Poor release is generally due to burrs and damage, rather than the finish in the cavity.

But I prefer and always buy only brass molds these days. No smoke, no bluing no oil needed....just clean golden shiny yellow brass!

Have fun!

[leadman]

I have found that the recent Lee molds cast better if the very shiny surface is dulled. I either use Comet and a nylon brush, a pencil eraser or purple power soap to dull them. Don't know why but it works and I get better fill-out.