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Joe Swenson

Making Madder Lake Question

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I know you mentioned this earlier in another thread or two. I am just wondering whether this is a surface effect in which pigment just settles out (down) on the varnish surface. Again, I cannot fathom how an aqueous solution can permeate an oil-based varnish. I can believe that this could happen in a spirit varnish. Nevertheless, it bears repeating in a controlled experiment. Again, thanks.

 

Sorry I wasn't clear, the color is extracted with alcohol. You can add a little water if the alcohol is too hot and dissolves the varnish. Try to work with a 'dry' brush.

 

I use tannin as a mordant. Too much tannin and your varnish will darken over time but will maintain it's clarity and transparency.

 

Tea is a good source of tannin because it also contains some oxalic acid which inhibits undesirable reactions with iron.

 

I hope someone corrects my chemistry if I'm wrong, since I'm only a lowly alchemist.

 

BTW if you hit red madder pigment with a base (ammonia)  it will turn purple, so pigments aren't immune from changes in pH.

 

Always experiment on samples before trying anything new on your instrument.

 

Oded

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Oded, I have messed around with this, and yes to me it is like mild chemical etching that creates the bond/adhesion.

Related to my post about sample boards for observation. Most all major coatings companies have sample boards from all their various colors as well as testing facilities that expedite the aging process in order to observe performance. My suggestion is so people can observe their own formulations over time.

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