40 year old dirt in carboy

[Brewer_Steve]

I got some old gear from my Grandfather.
One of the items is an old 2 gallon carboy that hasn't been used in 40 years.
There is some kind of dirt in there an nothing has worked to get it out.
It looks like a tea spoon of maple syrup or something on the side.

I've soaked in a strong bleach solution for a week and that didn't work.
I used oxiclean at the recommended dilution for a 2 day soak.
Then I dumped it and tried oxiclean at double the recommended dilution for 2 more days and it didn't help.
I've bent a bottle brush and started scrubbing it, but it isn't improving.
When I slide the tip of the brush along the side of the carboy, I feel a lump when I hit the stain.

Any suggestions for cleaning this?
I was thinking I'd try some muriatic acid, but I'll have to wait to spring so that can do that outside.

 

[BrewinJack]

take about 2lbs of sugar dissolve it in warm water and then add some bakers yeast... yes this is nasty hooch, but it will ferment out in about two weeks and the bubbling action will break up the dirty and nastys there, and the aclohol will kill any remaining bacteria... I did this to clean a 3 gallon glass carboy and it worked wonderfully... or it mostly will. After that dump it out and bleach and sanitize as regular. that should work. Dont drink it after its done

Cheers

 

[EdWort]

Hot Tap water and 1/4 cup of PBW. Let soak for 24 hours, rinse, then repeat.