Using white lead paste for seam cement

[Captlen1]

I am restoring a 54 ft Berthon boat and noted the seams were filled with white lead was wondering if any one knows the mixture of white lead paste and compounds needed for the mixture to harden.

 

[stephenh]

The white lead paste usually has lumps in it because someone forgot to ram the lid of the can home when it was last used and so you have to beat it up with lots of linseed oil to make it smooth enough to go in the seams but with so much oil it’s too thin and so you add some whiting powder to dry it off, unfortunately this makes it go off too hard so you add a dollop of axle grease to make it more elastic but this means it won’t ‘skin’ and the painters will be after you so you add some terebin dryers which makes it skin too quickly and you reach for the linseed oil to slow it down…………………

Good luck

 

[Grajan]

Stephen, that's trade secrets you have let out of the bag!!!!

 

[Victorious]

Tis my understanding that white lead was used above the waterline because red lead would often leach through the paint.
Paints are much better now, And red lead is a lot cheaper

 

[Seagreen]

So what's the mix for red lead paste below the waterline? Can this be used as a fairing compound. I have quite a bit to use up.

 

[Billy_Mizzen]

I use 10 parts linseed oil putty to 1 part read lead powder with a liberal finger full of grease to keep things flexible!

 

[Seagreen]

Cheers. I'll add that to my recipe list. What type of grease, though? Standard automotive or something different? Will a thinning of linseed oil do instead? I've quite a bit of that too.

 

[stephenh]

Found this -
Whiting putty shall consist of a mixture of whiting and linseed oil and shall contain not less than 12•5 per cent. by weight of linseed oil. Any colouring matter used, together with any impurities in the whiting, shall not exceed 5 per cent. by weight of the whiting.
The above is ordinary glazing putty
White lead putty shall consist of a mixture of whiting, white lead and linseed oil. The content of white lead shall be not less than 8 per cent. and not more than 12 per cent. by weight of the whiting. The putty shall contain not less than 11 per cent by weight of linseed oil.
The topsides putty we used to make was at least 20% white lead + a dollop of grease
Red lead putty shall consist of a mixture of whiting, red lead and linseed oil. The content of red lead shall be not less than 3 per cent. and not more than 5 per cent. by weight of the whiting. The putty shall contain not less than 12•5 per cent. by weight of linseed oil.
This sounds like Billy M's mix

Grease type ? - whatever you have most of.....and no, linseed oil is not a replacement for the grease.

 

[Seagreen]

Whiting? What is this? Will this mixture skin over and be usable underwater?

 

[stephenh]

Whiting is ground chalk - mix it with linseed oil and you have standard glaziers putty which, as I'm sure you know, goes off rock hard.
Add white lead to it and it stays softer, also stops it shrinking so much. Add some grease ( just a little - see above) and it stays elastic longer. And yes it is fine for underwater.

But... white lead is expensive, red lead is cheaper so as Bill M says use the red stuff underwater but not on the topsides as it tends to bleed through - see above.

 

[Seagreen]

Got Red lead, so that'll be sorted then. Cheers.

 

[Captlen1]

Bondo is full of talc and it desolves in water there must be something better than whitting to protect the seams?

 

[stephenh]

What's 'Bondo' ??

later edit -

ahh... found it ( thanks google)

"Bondo is a polyester resin product that when mixed with a hardener turns into a putty which then sets and becomes rock-hard"

and should never put in seams.