I think I found out why the Easy Off window cleaner worked well for
touching up dry paint, and I've got a guess as to what that "cottage
cheese" stuff was.
1. What was in that window cleaner that made it work well on latex
I think Easy Off Window Cleaner is still available as Easy Off Glass
Cleaner. I think they just changed the name.
I downloaded the MSDS sheet for Easy Off GLASS Cleaner (rather than Easy
Off Window Cleaner):
and it's got a solvent commonly called PnB in it. The MSDS sheet says
it has 2.5 to 10 percent PnB in it, 10 to 20 percent ethyl alcohol and
the rest would be water (which doesn't have to be listed on the MSDS
because it's not a potential safety hazard).
That MSDS sheet calls one of the constituents of the glass cleaner
"2-Propanol, 1-butoxy-", but it also gives it's CAS number as 5131-66-8,
and if you simply Google CAS 5131-66-8 you find out that it's a common
industrial solvent called propylene glycol n-butyl ether, or PnB for
'5131-66-8 | CAS DataBase'
(There are different chemical naming conventions so a chemical can be
called many different names, so the CAS system was developed to assign a
numerical code to each chemical so that different kinds of scientists
that use different naming conventions can all talk about the same
chemical by just specifying it's Chemical Assay System, or CAS number.
Google the CAS number and you find all of that chemical's aliases.)
All of the major chemical companies make PnB and sell it under their own
trade names. Dow has Dowanol, Arco has Arcosol, BASF has Propasol, etc.
If you can't find Easy Off GLASS Cleaner, then look under "Chemicals"
in your yellow pages phone directory and phone around to find out who
sells PnB in your area, and who they sell it to. The company that
purchases it will hopefully give you some if you toss a $10 bill in that
company's Christmas Party Fund. According to Google, Wal-Mart and
Staples sell Easy Off Glass Cleaner.
The PnB is important because PnB is also used as a coalescing solvent in
So, spraying some PnB dissolved in water on dried latex paint would
soften the paint, and allow it to self level again as the PnB and water
(read the PS below to find out what PnB (or any coalescing solvent) does
in a latex paint)
2. What was that cottage cheeze stuff?
Next time, don't use any detergent when washing out your brush. What
I'm thinking is that those blobs of cottage cheeze were the coalescing
solvent in your primer/paint mixing with the detergent you used to clean
the brush with.
Latex paints have water soluble coalescing solvents in them, and
detergents are also soluble in water. Both are soluble in water only
because one end of the solvent or detergent molecule is polar and is
attracted to polar water molecules.
What I'm thinking is that the water soluble ends of the solvent
molecules were attracted to the water soluble ends of the detergent
molecules and the result was something that had the NON-water soluble
ends of those molecules sticking out on both sides, thereby making stuff
that was insoluble in water.
Maybe try buying a new (but inexpensive) paint brush (with no cottage
cheeze in it to begin with) and paint something with that same
primer/paint, and then wash the brush out thoroughly without using any
(I'm also presuming that this was softened water from your city's water
supply system and not hard water from a well that you were using to
clean the brush.)
PS: Why do you need an industrial solvent in latex paint?
Welcome to Latex Paint 101:
Latex paints don't have any rubber tree sap in them.
Latex paints are a SLURRY (solids suspended in liquid) of tiny hard
particles of clear plastic (called "binder resins"), coloured solid
particles (called "coloured pigments") and white, clear or transluscent
solid particles (called "extender pigments") suspended in a solution of
a low volatility solvent (called a "coalescing solvent" or "coalescing
agent") dissolved in water. So five things: three kinds of hard
particles suspended in a solution of a solvent dissolved in water.
(There are also chemical additives in latex paints like mildewcides
and defoamers, and but let's just ignore those. They don't play any
roll in what the coalescing solvents do. )
When you spread latex paint on the wall, the first thing that
happens is that the water evaporates, and the tiny plastic binder resins
find themselves surrounded by that coalescing solvent at an ever
increasing concentration. The coalescing solvent dissolves (kinda)
those plastic binder resins, making them soft and sticky. The adhesion
of the paint to the substrate occurs when the binder resins are soft and
The same force of surface tension that causes tiny droplets of
water to coalesce into large rain drops in clowds then takes over and
causes each soft sticky binder resin to stick to and pull on it's
neighbors. The result is that all those tiny plastic resins "coalesce"
to form a continuous soft film sticking to the substrate with the
coloured and extender pigments suspended inside that film very much like
the raisins in raisin bread. The coloured pigments give the paint film
it's colour and the amount and coarseness of the extender pigments
determine how rough or glossy the paint film dries to.
As the clear plastic binder resins coalesce into a solid
continusous film, you no longer have gazillions of plastic/water
interfaces (which previously reflected and refracted light like
miniature prisms). Your eye sees light of all different colours as the
colour "white", so as the clear binder resins coalesce to form a film,
the amount of white light coming from the drying paint diminishes, and
so the paint appears to darken as it dries. That is, latex paints
darken as they dry for exactly the same reason that snow loses it's
white colour as it melts to form water.
Then, the coalescing solvent evaporates from the paint film,
filling the room with that freshly painted smell. And, as the
coalescing solvent evaporates from the soft, sticky plastic film, that
clear plastic hardens back up again to the same hardness as the original
plastic binder resins were when the paint was still in the can.