How to fix this mold

[Gtek]

I would not toss it, I have several that were no good for a good boolit. What bore size do you play with, drill cavities to a couple over of that size and next boolit run make you twenty or so pure lead slugs. Then you have them in stock ready to measure something.

[405grain]

There will always be a cost vs reward aspect on a repair like this, but sometimes it's just fun to tinker even if things don't work out in the end. Give it a try and see if you can fix it. If it turns out to be non-functional, then you can always buy a new one. Others have given good advise on methods to clean up this mold. I'll only add one thing, and you can try it or not because at this stage you've got nothing to loose. Before you try any repairs try sticking the mold into boiling water for about half an hour. This will convert most of the red rust into black rust (same as doing a rust blue). It will make any repairs that you do later a little bit easier.

[JonB_in_Glencoe]

Well, it's hard to tell if the cavities are pitted or not?

I'd soak the blocks in Ed's Red over night. Then brush with toothbrush, or better yet, a stiff nylon cleaning brush...HF has one in their "kit" of cleaning brushes.

Once the blocks are as clean as you can get it, use emory cloth to clean up the Sprue plate.
THEN, I'd cast a few, then use one of those to Leement the cavities.

Then cast some more...you'll know at that point of the mold is junk or not.
Good Luck

[high standard 40]

There will always be a cost vs reward aspect on a repair like this, but sometimes it's just fun to tinker even if things don't work out in the end. Give it a try and see if you can fix it. If it turns out to be non-functional, then you can always buy a new one. Others have given good advise on methods to clean up this mold. I'll only add one thing, and you can try it or not because at this stage you've got nothing to loose. Before you try any repairs try sticking the mold into boiling water for about half an hour. This will convert most of the red rust into black rust (same as doing a rust blue). It will make any repairs that you do later a little bit easier.

This is good advice. I agree.