Ether Jones wrote:
Norminn wrote:


Paint stores have product specifically for thinning both types of paint and
which don't weaken the film.


"doesn't weaken the film" is the part I want to understand better. Why
doesn't this product "weaken the film" but water does? I'm not saying
you're wrong, I just want to understand how it works.


Guess it contains the binder, so without as much heavy, ground up
pigment your paint will be as strong but with less pigment per volume.

Paint has three essential functional products (sometimes lots more
chemicals): pigment, binder, vehicle. Pigment is the color you want.
Usually ground up stuff. Binder is what holds it together when it is
dry. Vehicle is what makes it liquid enough to get from the can to the
brush to the surface, and makes it run out flat. The pigment, without
the binder (or thinned too much) would make it like milk of magnesia,
white dust on the siding )

The logic in not thinning too much is that
you dilute to the point that you are applying little more than colored
water.


So... it doesn't matter if I thin the latex 50/50, as long as I apply
enough coats that the total amount of latex I use is the same as I
would have used if I didn't thin it?

Quality paint rarely needs thinning. To thin it too much is to weaken
it's ability to stay on securely.

For example, say I pour out two equal portions of unthinned latex into
separate containers. I paint one board with 2 coats using the first
portion (using it all up). I thin the second portion 50/50 with
distilled water, and paint the second board with that, applying coats
(and letting them dry) until the second portion is used up. Both
boards now have exactly the same amount of pigment and binder on them.
Will the paint on the second board fail because I thinned it? _Why_?
(It's the "why" part I am seeking to understand).

Well, try this: take four boards, each 12" wide by four feet long. Cut
them in one foot lengths. Lay the 16 pieces of cut boards in four rows
of four. Should cover 16 square feet. Now pick them up, throw away 8
of them. Use the remaining 8 pieces to cover the same area.

Your thinned paint has binder spread too thin, I'm thinking. Might work.

Here is a link to additives, Floetrol (water base paint) and Penetrol
(oil base). Penetrol is only one I have tried, for spraying. Works
beautifully.

http://www.o-geepaint.com/cgi-bin/Fr...ww.floodco.com