New member with buried treasure

Good day. I’ve signed up to this forum to ask some questions. I have no experience with old printing equipment but I found some old printing plates dating back to the 1930s buried in a field.
Backstory… my family farms in the Cambridge, ON area and we own a piece of land which once belonged to the owner of a local foundry. A few years ago we were digging with the backhoe and something caught my eye. It was a rotted out steel box containing 20 printing plates advertising products from said foundry.
My question is in regards to cleaning. Some of them are in excellent condition, some are very stained. One has a thick layer of fossilized paper obscuring most of the image. What is the best way to clean these plates? I don’t know what type of metal they are made from, maybe lead or an alloy? What types of chemicals or solvents would be harmful to them?
My apology if this is the wrong place to ask this, but I appreciate any advice I can get.

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Finding and cleaning old treasure can always be fun.
Do define your objective. Do you just want to see them clean, or do you wish to print with them?
They are probably a lead alloy. Long on the lead. They could be zinc.
Start with some laundry detergent or some dish washing soap from under the sink and a stiff nylon brush.
If something more is needed, use a rich solution of TSP and more of the brush.
If you get off all the surface stuff and are left with metal with a white coating, it is lead oxide. The best way to remove that is with a brass brush.
To pay your dues here, show before and after photos.

Thanks for the tips Inky. I tried to add a picture to my post but it didn’t show up. I’ll try to figure that out.
While making prints with these would be fun, I’m more interested in just cleaning them up for display. Or maybe to sell if there’s a market for this sort of thing.
Thanks again for your help.

I don’t live far from you, and I volunteer in the 1860’s print shop at Westfield Heritage Village in Rockton. If you would like, I can stop over sometime when I am over your way, and perhaps come up with some ideas. I’m retired from being in printing all my life. You can contact me by my email which is obtainable through this website. It would be interesting to see what you have,


That sounds great. I really appreciate your offer. I haven’t been to Westfield for years, but I love studying local history. I’ll send an email and we’ll get something set up.

Meanwhile, try this link…!AhFSEPtzO6KixgdC3nxdnpuptfNq
If it works, consider these the before pictures.

Thanks, Huck

Hi there… I live in Galt, and am a printer as well. I don’t have much experience with cleaning cuts however I was intrigued with what was on the cuts. Looks like “Bibby built soil pipe” some very quick google work led me to a website for Bibby Ste Croix. In their about us and history pages, I found the following “1933 Bibby Foundry in Galt, Ontario, is founded by Ed Bibby and produces soil pipes and soil pipe fittings for plumbing in buildings.” I guess these cuts were used as advertising or marketing collateral for this foundry?? Interesting stuff… would also be interested in seeing them in print. Please post!

Thanks for the note. I’ll definitely keep this updated as I make progress.
If anyone tried and couldn’t open the other link you can try this…

Thanks again for everyone’s interest.