Red Lead vs White and OK for Topsides (hull above waterline)

[swiseman]

Please forgive me as a new user that I relize now I should not have interrupted Mr. Lodge's question with my own long list! Again please lease forgive me.?

Although my wooden boat is strip planked it sounds like this would be great for the keel to deadwood and other non-glued seams. I have just replaced the deadwood in White Oak from one log, portable saw mill sawed. I have white lead putty from Kirby here in the states. Would this be okay for below waterline? I called "DAP" who make our putty called "Glazing Compound 33" on the can and they said it was Calcium Carbonate, Whiting (talc?),Linseed, Soy and Mineral Oil and Mineral Spirits. Does it sound like your type of putty? What is the difference between the two lead products besides the color? I used red lead paint for the bottom which sounds like I'm headed in the right direction but Kirby doesn't list red lead powder? If I ned the red lead, I'll order it from one of the sites you guys kindly posted. Finally, would it be a good idea to mix some of the white lead paste, thinned, to a newer primer/undercoater such as Interlux (International) PreKote for the topsides?? That way the primer/undercoater would be the same color.

You guys are great! Thanks for the help,
Best, Steve

 

[tillergirl]

Good question. I always assumed that white lead was used above the waterline because of the tendency for lighter coloured paints on topsides and therefore less risk of the colour leaching through. Since you got no answers, I've tried researching the difference with limited success. They are in fact different other than the colour. Red Lead is Lead tetroxide, White lead, Lead carbonate. Red Lead is consistently referred to as resistent to seawater whereas the references to White Lead make no such comment. Red lead was used as a main ingredient in protective coating for steel etc because of its resistent properties whereas White Lead was used up until the 19th century as the first white pigment. Red lead clearly has uses as a pigment (it is still used for artists oil paints - I get my supplies from artist's shops) but the main reason for it being in paint is for its resistent qualities as far as I can discover.

Why is it used in putty though. I have always understood this to be because it creates a much stronger product that plain putty but I can't find anything to confirm this. Neither can I find anything to confirm my understanding that white lead is used above the waterline to reduce the effect of leaching. However, it does seem from what I have read that red lead is more resistent than white lead hence its use below the waterline.

I guess when you are mixing white lead with your paint you are reversing the process that has been occuring in recent times with the elimination of lead from paint because of its toxity. I think I favour towards the view that you don't need to mix lead with modern paints. Adding it to putty for stopping is one thing - ie putty is not good as stopping under the waterline without it (but I have no authority for saying this), but that doesn't mean you get any extra benefit from adding it to the paint - and logic suggests that if you want to get extra benefit from it in terms of resistence to seawater then it ought to be red lead not white lead which has only been used in paints for its pigment qualities.

There is also the point that we have no idea how the lead will react with what's already in the paint. White lead is described as reacting with some substances to go flakey.

What's in our putty - my recipe book says to make putty add boiled linseed oil to crushed dried whiting and knead well. What's whiting - I don't know. But then I don't what talc is made of either!

Hopes this helps. Perhaps others will have a view.

 

[swiseman]

Dear Tillergirl,

Sorry for delay as I was out on a family emergrncy during our Thanksgiving Holiday. Thanks so much for the kind reply and much appreciated research - your comments make good sense and if anything it sounds like I should just use a redlead primer as the bottom or else use the recommended prepared coatings. It does appear that the white lead was indeed a good pigment as well as has at least some predervative characteristics since our colonial timber sided buildings from 200 years ago lasted realitively well even though they were of White Pine. Of course the timber was virgin and very mature then as well.

Thanks Again,
Steve

 

[cliffordpope]

I have always understood that the almost unique value of red lead is its power to bond to wood. So that is why it is traditionally used in the most arduous circumstances, eg under water. Also when added to putty it helps to make the putty stick too.
I have also read that it is advantageous to mix a proportion of red lead into white lead primer, for the same reason.
Red lead will also bond to iron and steel. An account I recently read of life on a merchant ship before the war said that all surfaces were firstly painted with red lead primer (hand mixed from powder and boiled linseed oil), then with a coat of 50/50 red/white lead primer, then 100% white lead, then several undercoats, then white gloss.
Incidentally red lead primer should not be mixed too long in advance of use, because it hardens even in the tin.