Revealing partly-effaced frame numbers

[groily]

Don't think it was on here and if it was I can't find it, but I'm looking for something I have read recently about ways of getting partly-effaced or removed frame numbers (that are invisible to the naked eye or with a glass) to reveal themselves.
Bright lights at funny angles and all that I have been through with moderate success -  it has got me about half the 'invisible' digits (to my surprise!) but not the rest. But I seem to remember something about chemicals coming to the rescue . . .???

Reason I ask is I've recently got myself a frame without papers for a project machine. I'd like to get a dating certificate for it from the appropriate quarter (it's a Velo Valiant) as a first step to 'legitimisation' - but it isn't looking too promising just now!

Grateful for any Good Ideas from anyone here who's been in the same situation.

[Roger (Doomtrainbarx)]

You and me both Bill - I've got a GA7 frame that I can't quite make out the full number

[Rex]

There's an acid solution that a mate of mine used on his pre-war BMW. If you're interested I can contact him?

[groily]

There's an acid solution that a mate of mine used on his pre-war BMW. If you're interested I can contact him?

Definitely interested Rex, could be what I might have read about somewhere. Don't want to 'be a trouble' as they say, but Thank You.
Very not urgent, as when I say 'project', in this case I mean it. It's a dinky toy really, but an amusing diversion from some of the normal (saner) stuff we do. 

Loads of other things to be going on with, and tbh might be a project that gets passed on to A N Other. Some supporting dox would be good, though, whichever way things go, and the frame number deciphered would be a v good start.

[Rex]

OK, I'll text him tonight and hopefully he'll reply ASAP. I know he's not been too well of late.

[muskrat]

G'day groily.
I had heard X ray is used so I googled it. https://www.google.com/search?client=firefox-b-d&channel=entpr&q=How+to+recover+erased+engine+numbers
Specific chemical solutions can be used to selectively dissolve the metal around the erased markings, revealing the original indentations.
One example is a solution of copper sulfate, water, ammonium hydroxide, and hydrochloric acid.
Cheers

[berger]

Bill as daft as it sounds i found a photo on a good camera [ not my old foggy one] helped me with a frame number it sounds silly but it worked better than me looking at it , so depending on how bad it is i would try it in good light.   now where's my black&tan

[groily]

G'day groily.
I had heard X ray is used so I googled it. https://www.google.com/search?client=firefox-b-d&channel=entpr&q=How+to+recover+erased+engine+numbers
Specific chemical solutions can be used to selectively dissolve the metal around the erased markings, revealing the original indentations.
One example is a solution of copper sulfate, water, ammonium hydroxide, and hydrochloric acid.
Cheers

That is just brilliant Musky - many thanks! And it certainly works, that potion. Obviously the way to go for me and for Roger I reckon!
Now, back in the day one could wander down to a paharmacy and get a bit of acid, etc  . . . but these days, not so simples! Couldn't persuade our local chemist to flog me half a pint of concentrated sulphuric when I bought a battery off Amazon that came dry charged but empty (can't post acid I suppose  . . .) - maybe they don't even have the right to keep the stuff any more. Oh well - I'll see what I can do!

[Rex]

Apparently it's called "Fry's Reagent" and is a mix of copper chloride and hydrochloric acid in a 2:1 ratio.
Try it at your own risk, I'm just passing the message along.

[groily]

Thank You very much indeed Rex. Ties in with the concoctions referred in the link from Musky too.
Risks noted!

PS Comes in standard and extra strength by the look of it. Not sure how easy it is for a non-commercial purchaser to get hold of it, especially the high end high cost 'macro' cocktail, but feelers are out  . . .there are suppliers listed for some grades at least.
Be nice to be able to get some cuprous chloride and acid and try to create the stuff oneself if it's not too dangerous! The guy in Musky's video link about Ballistics serial number recovery was merriily swizzling stuff around and lived to tell the tale anyway.

[sean]

back in the early 70s the police used a solution of ferric chloride and distilled water and I think a black light  to show engine numbers on aluminum cases that had been ground down thats about the time Triumph came out with the little triumph stamps on the engine number boss .
its funny because you could still buy new crankcases from the dealer with no engine numbers , I think the dealer was supposed to stamp the numbers but I remember buy a left side case from a dealer and they never said anything .