In the mid 40s when my old man was apprenticed into the family painting company his first job was to take the bus to the local paint suppliers and bring back (in 14lb consignments) semi prepared oil paint. If he was polite the chap in the shop would wrap the wire handles in lining paper so they didnt take his fingers off on the way home.
The lead content was that high it used to putty up in the bottom of the cans and on his return to the yard the old boys would roll their sleeves up and kneed the lead back into the oils before even thinking about using a stick. Needless to say none of them had any hair or teeth and the poison would send them a strange colour.
It was then used to make paint by mixing it with oils, dryers, dyes and spirits In various combinations depending on its use. Primer, undercoat, topcoat, timber, steel etc etc. This is how they did it before DIY. One of the reasons a painter had a 7 year apprenticeship.
Primer for instance must be made slightly more oily and much thinner than undercoat. It has to go on fast and be cheap.
The problem with bare steel was, even if you got a coat of primer on it before it began oxidizing, within hours of becoming damp the tell tail signs of rust coloured blotches would start to seep through the porous primer. It wasnt until the undercoat and top coats sealed the steel that the bleed through stopped.
Thats why they they coloured it with oxide pigment. It didnt add anything to the paint apart from colour to hide the bleed. That way a steel beam could be lashed in and sent on its way and it still looked new when it arrived on site. The lead content was controlled by the painter and it wasnt cheap so very little was used.
Later when suppliers and shops began selling ready made paints, red lead was fantastic. It had a high lead content but was expensive compared to simple primers. Because of this industry tended to stick with red oxide primer. That is, simple primer in rust colour.
It makes me smile when people say Oh yea I took it right down to bare metal and gave it two coats of red oxide and a coat of ______?
So you blathered on a couple of layers of the cheapest porous crap available, missed out an undercoat system and hoped the top coat would do all the hard work.
Priceless.
