Cleaning up an aluminum mould

My dad used to cast his boolits all the time when I was young, he loved Lyman moulds and I used to watch him put them in hot dish soap water and clean them with a toothbrush, then dry them off and put them in the oven for about 10 mins, then when they cooled off he would oil them up and put them away. Well I really like the NOE moulds, and even though they’re aluminum I still clean them after every use the same way my dad did, but one of my moulds has a little discoloration, and I’d like to get that off so it will be shiny again, the washing drying and oiling keeps them working great but it doesn’t take any discoloration off the mould, so what’s the best way to remove any discoloration?
Thanks,
Paul

There is no reason to do what you're doing. Aluminum doesn't need to be oiled as it doesn't rust.

If the discoloration is on the outside you could polish it out with a polishing compound. Something like Flitz or even an automotive product. If its on the inside I would leave it be.

I spray my aluminum molds with oil but mostly for the steel sprue plate and screws. Whatever gets on the aluminum gets left alone until I'm ready to cast again.

If the discoloration is on the inside ... maybe in a boolit cavity ... that could be a "patina" that you do not want to scrub off .
Aluminum moulds do not need to be "oiled" the oil contaminates the cavities and must be removed .
So you start the cycle all over again ... clean with water ... oil ...and again
I prefer to keep water away from all my moulds ... clean them with acetone and a toothbrush or acetone and a Q-Tip . Before putting away protect with a dry lube , any brand will do , spray on or liquid . Dry lubes containe micro-Teflon particles in a alcohol carrier ... it doesn't contaminate cavities ( acts as a mould release agent ...Teflon is slick) and protects steel parts from rust and aluminum from corrosion . Got water and oil beat seven ways from Sunday .
Try it just one time,
Gary

You are wasting your valuable time! A mold only needs to be cleaned when it is brand new to remove manufacturing gunk from it.

I NEVER clean my molds. They just do not get dirty. And who cares what the outsides look like. That has nothing to do with the cavities and the quality of boolits you are dropping.

Only lube you will ever need is blue 2 cycle motor oil from Walmart - - -just a drop on the sprue plate screw to help with movement. NOT in the cavities.

Aluminum does not corrode or rust. Unless you spill acid or caustic on it.

God Bless your Dad, but forget what you saw him do after every casting session!!!!!.

once they are casting well i leave mine alone and just cast away .never cleaned mine apart from when i first got them.

I have had all if my aluminum molds damaged by water. they corroded in the box on the exterior of the blocks, with some corrosion on the mold faces. Luckily the cavities remained unhurt.

water from storm damage was the culprit.

I bought a used mold (older 6 cav Lee GB mold). The previous owner boiled it. The boiling discolored the aluminum. I tried several non-abrasive techniques to clean it...all failed. I just learned to like the discoloring...That is my suggestion to you.