Flash Rust??

[Brokenbear]

I have bought 4 or 5 new to me used Lyman molds in the last couple of months ..
All were seemingly very well cared for ..nicely oiled and plastic bagged ..cavities and mold faces slick as a baby's butt and just a hint of speckling of the metal on the outside ..
So I fired up today and limbered up 2 of the molds going over them with Iso alcohol using Qtips n paper towels
As I started heating them on the top of the pot I noticed one sprue (top side) plate turning kind of charcoal color and texture

After cooling.. that sprue plate top became a distinct rusty orange ..
It may or may not be rust ..and I may have missed cleaning it with alcohol and is just baked on preservative of some sort

For those of you I am boring ..please understand I have searched for this phenomenon to no avail

So the question is cleanup ..thinking a brass brush and denatured alcohol on the outside and cotton cloth on the inside (Insides seem to not have shared whatever happened to the outside) and of course the whole idea of this post is to improve my present perceived course of action

Bear

[Winger Ed.]

It's rust all right. But it's on it more so than in it.
This early in the game, it should wipe off with a oily rag.

[fc60]

Greetings,

Did you use 99% Isopropyl Alcohol? The 70% and 91% contain oils.

Cheers,

Dave

[Brokenbear]

So is a brass brush a no no as I think this crud is heavier than just powdery ...?

I used 70% but am switching to denatured alcohol ..

[405grain]

A brass brush should be OK for scrubbing the outside of the mold blocks, and the sprue plate, but not the mold cavities. You can use an old toothbrush to scrub the mold cavities. There's a product called Isoheet that you can get at most auto parts stores, (and the automotive section at Walmart). Isoheet is 100% isopropyl alcohol and is used as a fuel additive. I generally use it to mix with some lanolin to make case re-sizing lubricant, but it's also a good source of pure isopropyl alcohol for other things too.

[blackthorn]

I get my 99% alcohol at Costco.