De-Rusting an Imposing Stone

As some of you already know we are in the process in moving a large 4x6’ stone into our shop. Before we move the metal slab into our clean-ish shop we wanted to de-rust it. Is light sanding with emory paper on a drum sander an acceptable option? Maybe a chemical rust converter? Or should we just slather the stone with oil and then dose it with some fountain solution? Thanks.

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It it were mine, i’d wipe it down with a mixture of say 25% petroleum solvent (diesel fuel, mineral spirits or kerosene) and cheap motor oil … i’d slather it down with that and let it sit a couple of weeks. You’ll be amazed at what that will do to clean it up. If it has a LOT of rust you can spray or brush on phosphoric prep and etch per instructions … from a big box home store ….

It might take a couple of applications.

It works really well.

I would not use any type of power tool equipment sanders as they will destroy the surface finish and possibly ruin the flatness.

You can scrub it with scotch brite.

xx rick

Hi, I cleaned up a 4 x 3 cast iron stone with WD 40 and using a round disc sander with wood sanding discs so as not to be too aggresive. Worked very well.

In order, specifically!, >Orbital Sander< with progressively finer Grit *Velcro* fitting, and then >Reciprocating Sander< with clipped on sheets of, progressively Finer Wet & Dry with spirit/decontaminate instead of water!!
With just a modicum of Science, not a lot, the Reciprocating machine assisted by a straight edge clamped and moved over progressively, WILL bring the Stone back to its original Milled, Machined, Fly Cut, Finish.??

We have used this method many times, occasionally substituting, water, on the Wet & Dry, with very fine grinding paste, it brings back the original machining marks on the face of the stone very well…
Including The lip, for registering Galley`s when sliding pages on or off.?

I wouldn’t go at a large surface like this with coarse abrasives.
Stick to 30 wt. oil, 00 steel wool, and some thick rubber gloves/elbow grease.

When you’re done, clean with acetone and some rags, and then paste wax the surface to preserve the finish, just like the bed of a cutter. You’re in FL, so unless you preserve the finish, it’s going to rust again.

Best of luck with it!

I did mine with an orbital sander. Came out fine!

I have to disagree with sandpaper. It’s too aggressive. I definitely have to disagree with sandpaper in an orbital sander, it will make more work than it saves. I have a piece of equipment that a previous owner used an orbital sander on, and the coarse-grit paper left curly marks that are too deep to be removed without significant work with the fine-grit paper.

If you want to make the surface factory-new, than you will probably need to go that route, but if you simply want a functional surface that works as good as new, then I have a suggestion:

First step: bulk rust removal. Soak the rust with kerosene or WD-40, then use a flat razor blade, the kind with the metal strip attached, to scrape the surface. It will save you a lot of work, and leaves no visible marks on the surface. Use the razor with a slicing motion, held 45° or so to the surface. The rust will shave off right down to the original surface. Buy a box of blades and work the entire surface this way.

Second step: Scotch Brite (purple, then green) + Kerosene. The razor will have taken care of the hard work for you, and the Scotch Brite will bring the surface back to bare metal. When using the Scotch Brite, apply pressure evenly with the palm of your hand.

There might still be some staining in the pits of the metal, but if function is what you desire, then you won’t need to worry about them at all.

With Respect and at 4`x 6 ` (presumably Feet rather than Inches?) implying that Coarse Abrasives MIGHT hurt is just a Tad alarmist surely!!.
As it must have originally come from a production house, (it certainly was not from a Hobby printer with an 8 x 5 Tabletop) at that size it would have easily accomodated chases and forme,s with 8,s 16,s even 32 pages up, e.g. for Big Tirfing,s Big Jo/Bergs, Big H/bergs, Big Millers etc etc.??
With Steel Chases at that size ripping into the surface of such a stone year after year, the Surface virtually NEVER suffered, The chases however DID!
Being Steel (Chases) it was a fairly frequent occurrence for entries in the Accident Book to read:- Finger(s) cut & treated by the First Aid(er) in House.
Long before H. & S. existed.
By implication it would probably need something with the abrasive power of a T.B.M. (Tunnel Boring Machine) to seriously effect that kind of surface.
It has been attempted to reduce (cut down) a slightly smaller stone by a few inches, but even with a 9” Cutting Disc in a powerful Angle Grinder and a Diamond impregnated Disc it was NOT easy, Hence Tad alarmist.??

Recently we Milled a channel, to make a lip on a Tiny Stone 12” x 14” for sliding made up pages On & Off.

Although the first attempt was with a Good Quality milling cutter U.K. origin, it snapped on the fist pass, only set to take off .001”
Eventually a *Swedish Sandvik* Cutter was used.

From the *Old* Horses Mouth, *Old* Printers Stones are very Hard.

If the rust is not too heavy, I have had good results de-rusting small parts with half and half vinegar and lemon juice. If you could lay the stone down flat and pour a shallow layer of the liquid on top, and then keep swishing it around with a Scotch Bright pad or steel wool, using light pressure, for an hour or so, adding new liquid every so often, I think there is a good chance it would work.

If you decide to try this method, I would suggest that you try it on a small area first, to see how well it works in your case. Then rinse with water, dry, and oil it right away to prevent it from rusting again.

P.S. I’m not suggesting this because I don’t like to use solvent. I’m suggesting it because it has worked for me. The only difference from what I have used, is that I have immersed the part in the liquid, and you are not going to do that, obviously.

You are dealing with acid, so be sure to use adequate personal protective equipment (eye protection, hand protection, etc.)

Let us know what you decide to do and how it turned out.

With mine same size on a wooden base of cedar. Underneath the stone in chalk - glasgow 1905. Well its cast iron. So I soaked it in parrafin (Kerosene) and scraped with a paint stripper. All the rust went. I’m a demon with an oil can and every time I walked past the stone it got a blast. Every time I washed a press up I’d give the stone a slurp! My theory is that its porous and once you get active it wont need attention. Some of these stones were planed to optical flat. Do not grind them under any circumstances unless damaged in a fire. Check with a straight edge, and then act.

look, don’t forget its meant to be perfectly flat. i was told that the UK ones were made in shipyards because they could metal plane, things like propellers and suchlike. Beds of presses too. Anyway don’t aggressively attack that surface. The rust in mine went down to level and has never been aggressive again. on the outskirts of my stone there are trays, odd jobs, interesting blocks etc, 4x6 is a big stone! With me I have used vegatable oil too, with great effect and a broad paint scraper.

A light duty Scotchbrite pad and some Evapo-Rust is what I’d use!


After you get it clean. Use Silicone or auto wax. Silicone would be better. Will seal it and won’t leave residue from the wax in the pores. The silicone is clear. Less effort just spray it and it dries.

I think paste wax has done well on the bed of my cutter, but I’m curious about the spray silicone you’re mentioning Theo; does it come off easily? Does it flake over time?

Silicon spray, at least what is sold by printing supply houses, is an aerosol liquid that leaves a thin film. No flakes. Printers also use it to reduce static.

Silicone never Flakes, It wears off the cutter, it’s used 8 hrs. a day. It’s even put on the blade and the part that holds the blade. Smooth cutting. Applied at night after shifts are done.
On the stone, no flakes. Isn’t applied often but All rust free. I polished it with the grain using a fine wire brush on the drill.
I just buy silicone from the big box stores.
I have even used it on Mag. cuts to avoid them deteriorating, washed it off with type wash. I also spray it on some type that I don’t used very often. Washed is off with type wash. Keeps it all from getting the powered rust that lead gets.
I haven’t tried it on my brass Ludlow matrix, after being cleaned, with Brasso.

A little story about silicone…..

When I worked for American Can Company years ago, I was visiting one of the can plants which made and printed aluminum beverage cans. Somehow we got talking about silicone. They said that if there was the slightest trace of silicone on a can, it wouldn’t accept ink. It was enough of a problem that the plant manager banned silicone from the plant.

This got me wondering about some of the mysterious problems which people have reported on Briarpress, with rollers and/or plates not accepting ink, and whether it might have been caused by traces of silicone on the surfaces. Just a thought….

I know that auto body people hate silicone lubricants, it’s damn near impossible to detect, just as impossible remove, but it shows up as voids in the paint.

And Theo, I was told (at least for Linotype mats) that the only part of a matrix that should ever be cleaned is the reference side, everything should be left as-is, or you run the risk of hairlines…

Hey folks,

Thanks for all the great input! We have decided to attempt soaking the stone with oil and using a large wall scraper to remove the rust.

If we feel it needs something more, we will try steel wool applied with a vibrating sander.

If still more is needed, we will degrease and use a chemical wash like acidic acid or prep-and-etch or the likes.

In the end we will wax

image: 50/50 oil and mineral spirits applied with garden spryer

50/50 oil and mineral spirits applied with garden spryer

Yeah, the persistence of silicone is a problem for inking surfaces, but here it would only affect the bottom of a form.

Progress with the stone. We oiled, and oiled, and oiled some more. Then used a “wall scraper” to remove the rust and used mineral spirits to buff to a nice patina. The next step will be to use a lapping block with crocus paper.

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