Barber Hone Residue

I bought a couple of old Carborundum hones off of eBay from separate sellers and found that both had identical oily black residues on them. I tried out the hone on a crap blade and found the residue to be sticky and resistant to honing motion. To eliminate the residue, I first tried washing it off with detergent and a green scotchbrite pad. That did nothing so I went ahead and started lapping it on a DMT 320. While I did successfully lap one side to smoothness and eliminated the residue, some of the black residue appears to have permanently transferred to the center of my lapping plate.

So, I have a couple questions.

1. What the hell is this residue? Has anyone seen this before and how did it get there?

2. Is there a better way to remove it? I'm considering alcohol (first, for the stone:w ) to see if that dissolves it. I have also tried rubbing the two hones together, since they are of similar grit but that seems to be slow going. Any other suggestions?

3. I was going to ask if there might be a way to clean the lapping plate but I would assume that would only be answered by whatever might work to dissolve the residue off of the hones. Since getting the crud on the plate, I have used it to lap a couple of other hones and the lapping had no effect on the crud on the plate. Anyway, I would welcome any suggestions for clearing the plate as well.

Some of the old carbo's were used with oil instead of water as a lubricant - it's my opinion that that is what you are seeing. I purchased three old carbo's and all of them looked like that. I used my Norton flattening stone to lap all three....it took a while, but it worked. Unfortunately, the carbo's are so hard that they virtually destroyed my Norton. It was brand new (only used a few times on my Norton hones) and when I was done with the carbo's it was only half as thick! Those are hard suckers.....but they hone nicely once cleaned up!

I was afraid that it was oil. I tried alcohol and paint thinner on the hones last night and it had no effect. I guess I'll just keep lapping away!
Thanks for the info.

Use "Fume Off" oven cleaner. That has cleaned up a bunch of hones for me.