red lead

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.
http://en.wikipedia.org/wiki/Prussian_blue
So - does anyone know anything about the use of red lead up until so late a date, and why it finally (and belatedly) gave way to prussian blue?
BugBear (curious)
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We were still mixing our own at the end of the seventies.
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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
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David Littlewood

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David Littlewood wrote:

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
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writes

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.
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Doug had written this in response to http://polytechforum.com/modelengineering/re-red-lead-11948-.htm :
The red lead produces a very thin / very fine film, normally for the final stages of scraping or fitting. It can be applied via a thin oil or for a very fine film alcohol can be used. It can also be used to coat one surface and bluing on the other surface, to enhance the contrast of points of contact. The bluing in oil is normally used first to mark because it produces a thicker film and provide more lubrication, protecting the surface plate or straight edge from damage. Hope that helps. ------------------------------------- Cliff Coggin wrote:

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"does anyone know .. why it finally .. gave way to Prussian blue?".
David
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David Littlewood

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On Wed, 5 Aug 2009 15:08:15 +0100, David Littlewood
Vorsprung durch teknik ?
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Chris Edwards (in deepest Dorset) "There *must* be an easier way!"
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David Littlewood wrote:

Splendid piece of editing, altering my question substantially.
BugBear
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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
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David Littlewood

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David Littlewood wrote:

Evidently.
*do* you have any idea why Prussian Blue didn't oust red lead sooner?
BugBear
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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
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David Littlewood

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David Littlewood wrote:

Ah, OK. I thought you'd simply misunderstood, which was the reason for my initial clarification.
BugBear
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bugbear wrote:

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.
--
Kevin (Bluey)
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On Wed, 05 Aug 2009 09:38:03 +0100, bugbear

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
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Mark Rand wrote:

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.
> whereas the

Do you mean the Stuart "Blue Stuff" or "Red Stuff" ?
BugBear (who didnt know Stuart did red stuff)
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