In my reading of older manuals and books, it appears that a red lead/oil mixture was used for marking/scraping up until (roughly) the mid 1930's, when the current prussian blue/grease mixture was adopted.
According to Wikipedia, Prussian Blue (the pigment)
*massively* predates the 1930's.BugBear (curious)
We were still mixing our own at the end of the seventies.
In article , bugbear writes
Don't know for sure but put forward two factors which may have been significant:
(1) Prussian blue has a very intense colour, probably visible in much lower amounts than red lead;
(2) Red lead (Pb3O4), like any lead-based pigment, is toxic, whereas prussian blue is not (despite being stuffed to the gills with cyanide ligands).
David
You've got me backwards; I wasn't asking why red lead was replaced, I was wondering why red lead held out for so long BEFORE being replaced...
BugBear
Don't remember using it for marking out and scraping , but I do remember using it for a lubricant on dead centers in the lathe. Some lathes had a little pot cast into the tail stock with a nib that fitted into the pot for the keeping of the red lead . A little dab on the dead center helped lubricate the centering hole.
Probably due to health concerns ,much like the omission of lead in paint products.
My apologies to Bugbear I inadvertantly sent a reply to his email address instead of this forum.
Possibly it was just another of those traditions that British industry was so reluctant to give up, despite all the evidence that there were better alternatives.
Cliff Coggin.
"does anyone know .. why it finally .. gave way to Prussian blue?".
David
I was using red lead mixture as a spotting medium last year. I have also used Stuarts Micrometer Brand red spotting medium as a contrast to their blue medium, but it is very sticky. The home-made red lead based medium is more controllable and can be used for very fine definition work. whereas the Stuarts stuff is better for improving contrast where the lighting is less than perfect.
White lead (lead carbonate) has been used as a high pressure lubricant. There are much better replacements to this such as molybdenum disulphide powder carried in a little oil or grease.
Mark Rand RTFM
Vorsprung durch teknik ?
--
Chris Edwards (in deepest Dorset) "There *must* be an easier way!"
Splendid piece of editing, altering my question substantially.
BugBear
That's interesting; Popular Science in the 1930's (thank you. Google books) speaks of red lead being used for coarse work, as a substitute for Prussian Blue.
Do you mean the Stuart "Blue Stuff" or "Red Stuff" ?
BugBear (who didnt know Stuart did red stuff)
No, I merely quoted the bit I was replying to, and removed the bits I wasn't. Maybe you didn't express your question as you might have wished.
David
Evidently.
*do* you have any idea why Prussian Blue didn't oust red lead sooner?BugBear
No, but I did on the other part of the question you asked (whether you meant to ask it or not), which is why I answered that and not the other.
Look, enough. I was trying to be helpful, if it upset you that is regrettable for you, get over it.
David
Ah, OK. I thought you'd simply misunderstood, which was the reason for my initial clarification.
BugBear
Doug had written this in response to
The red lead produces a very th> "bugbear" wrote in
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