Using mould prep

[kcajeel]

I'm new to casting and would like to hear from the experienced about using mould prep or other items like that on my moulds.
My fatherinlaw has casted for years and is really good at it. He cringes at the mention of anything like this. But I have also seen some of his moulds with some rust in them.
Thanks for your views.

[gray wolf]

Mold prep is before the fact and rust is after the fact.
Some folks use products to help release the bullets from a mold, some work and some don't.
They have been known to change the size of the bullets that the mold drops because they coat the inside of the mold. I don't use them. If a mold drops nice bullets and they release from the mold without to much difficulty then don't put anything inside the cavities.
If you have a mold that gives trouble with sticking bullets there are ways to fix it.
You didn't ask about a problem so I wont take up the time going into all the fixes.
As for the rust -- I would think it would be more of a neglect issue. Proper care should be taken with a mold or the parts of a mold that are prone to rust.

[theperfessor]

Is mold prep needed to cast good bullets - No. A clean mold with no burrs that is at the proper temperature will cast good bullets. If the bullets don't drop out then check out one of the many threads here about lapping mold cavities.

Do you need to do something to prevent ferrous molds from rusting between casting sessions - maybe, maybe not, depends on the storage conditions. Some people use Kroil, others have more elaborate solutions. I just store mine in my gun room in the house where the temperature and humidity are controlled, haven't had any rust yet.

[dromia]

Good advice from the two previous posts.

If I feel the need for mould prep they I'll try and find the source of the problem and fix it rather than "hiding" it with mould prep.

As to rust well thats ultimately down to how you store your moulds and the conditions they live in.

I don't oil my moulds for storage and I live in soggy Britain, I check my moulds regularly and the only rust signs I've had has been on sprue plates, no rust on the metal mould blocks.

Oiling iron moulds is a good precaution as rust can kill them but my modus operandii is always less is more, if things are working then don't fix it. If moulds are casting well then I don't want to spoil that and I can get away withut oiling but I'm aware that I do need to check regulary to head of any trouble.

[Bret4207]

Don't put anything in the cavity. Any rust can be dealt with by scrubbing with an abrasive item like a typewriter eraser ( if they still make them), a bit of abrasive cloth or steel wool on a wooden stick or by incredibly careful scraping with a proper tool. A little rust won't kill a mould, but it will cause acne on your boolits finish, sometimes cause release issues and sometimes make zero difference. One of my favorite moulds is a discontinued Lyman 311316 that I tried coating with paraffin. Moisture got under the wax and rusted the mould. After much wailing, gnashing of teeth and rending of clothing I found that the mould still casts fine, but the boolits have zits.

[DLCTEX]

I bought a mould off Ebay(Lee 476-400) and when it arrived yesterday it was covered with gray mould prep. I tried casting with it and The boolits were sticking in the mould and were rough on the surface. I removed the prep with acetone and the boolits now drop freely, are smooth, and are .001 larger. Makes me wonder why the owner ever preped it in the first place. The top of the mould showed galling, but after using Bullplate lube it looks much better.

[462]

kcajeel,
Welcome.

Listen to your father-in-law.

I was given an old Lyman mould with rust-pitted cavities. Boolits literally fall out of the cavities and the target has never complained about the few blemishes.