[Leica] Painting cameras, the ALPA black crackle finish

[jackherron at cox.net (Jack C. Herron)]

Even more off-topic!

    Paints consist of basically two things;  The first is the vehicle, a 
liquid which binds the pigment and adheres to the base.  The vehicle must 
harden and become impervious to the environment.  This may be due to the 
evaporation of the solvent (lacquers) or the oxygen assisted polymerization 
into a solid (linseed oil).
    The second is the pigment, which gives color, hiding power and other 
characteristics to the vehicle (originally powdered minerals, such as 
ocher).
    In any event, a layer of liquid paint first forms a skin, like that of a 
cooling pudding, over a layer beneath which is protected from fast 
evaporation or oxidation by the skin.  It takes much longer for the solvent 
to profuse through the skin, or for enough oxygen to diffuse through the 
skin to harden this protected layer.
    In wrinkle finish paint, the skin floating on the lower layer is 
expanded by the second coat before the second coat can become solid.  Since 
the skin is now larger than the base,. it solves the problem by pushing up 
the excess into ridges, much like the formation of mountains on the earth.
    In crackle paint some of the pigments are designed to float to the 
surface of the liquid coat, and the vehicle is chosen to have high shrinking 
powers as it dries.  In this case the pudding skin becomes smaller than the 
area covered, aggregates into islands which pull part from each other, 
leaving boundaries of the second layer, rather like tectonic plates on the 
earth pulling apart.  Since some of the pigments have floated while in the 
liquid state, these bottom layer boundarys have a different coloration from 
the islands, creating the visual effect.
    In the hammered finishes powdered aluminum (one of the pigments) is set 
up to aggregate in a somewhat similiar but less pronounced effect and 
creates a finish which resembles hammered metal.

    Even in my town (500,000 population) it is sometimes hard to find 
wrinkle finish paint as it is a bit of a speciality item, but I have found 
it in large paint stores and large art supply houses.
    A quick Google search reveals that it is also available in red, and 
frequently found in automotive stores.  The first page revealed no vendors 
on the net, but-
http://www.eastwoodco.com/
a company which carrys auto restoration supplies has a wrinkle finish paint, 
#10014 Z, 12 oz aerosol can, $10.99, under specialty coatings- underhood 
coatings.  I have not used this product, but most of Eastwood's products are 
normally of high quality, as their clientele must be reasonably affluent to 
assay the $100,000 restoration of a classic automobile.

"Keep pushing the paint can button---"
Cheers,
"At my age, nature is wrinkling me!"
Jack
Jack C. Herron
8118 E. 20th St.
Tucson, AZ 85710
520 885-6933