Originally Posted by painter84
So am going to help paint a friends bedroom and i have a few questions, any advice would be kindly recieved. The walls are split into 3 colours Top is white, middle is light pink and the bottom is a darker pink. I think they have decided on a beige colour and one of my many concerns is that the darker pink might show through!?!
There are several things you can do to improve the hide of the beige paint:
1. All else being equal, flatter paints will hide better than glossy paints, and
2. All else being equal, inorganic pigments hide better than organic pigments
When the colour of the substrate shows through a paint film, what's actually happening is that incident light is making it through the paint film, reflecting off the substrate, and making it back out of the paint film to your eye.
The reason why flatter paints hide better is because they contain more extender pigments which reflect and refract light, thereby making the incident light take a longer and more tortuous path through the paint film. That increases hide because more incident light is absorbed along that longer path, and so the amount of light that your eye sees that has reflected off the substrate is significantly reduced.
Each of the "colourants" in the paint tinting machine consist of glycerine with coloured solid particles called "pigments" suspended in it. They use glycerine as the carrier fluid because it's equally miscible in both mineral spirits and water, so the same colourants can be used to tint both latex and oil based paints.
The colourants can be divided up into two groups; the organic pigments and the inorganic pigments.
The organic pigments are the colourwheel colours, like red, yellow, blue, green, magenta, orange, purple, etc. Basically, the colours you find on a colourwheel are all organic colours, and in general don't have very good UV resistance or opacity.
The inorganic pigments are best thought of as the synthetic equivalent of the pulverized rocks that artists have been using for millenia. These include:
a) Yellow Oxide (which is a mustard yellow colour and is the synthetic equivalent of Raw Sienna, named after the Italian village of Sienna where the soil and rock have a mustard yellow colour.)
b) Red Oxide (which is reddish brown in colour and is the most common form of iron oxide.)
c) Brown Oxide (which is yet another iron oxide and is the colour of chocolate brown.)
d) Raw Umber (which is a very dark brown that can almost be mistaken for black).
e) Black (which is actually ordinary soot. It's made by burning natural gas in special furnaces with insufficient oxygen to produce copious amounts of soot.)
f) Titanium Dioxide (which is white in colour. Titanium dioxide is what replaced lead carbonate in 1974 when lead based compounds were banned in house paints. You can still buy lead carbonate as "Flake White" in art supply stores.)
Basically, all of the colours (except black and white) that you can imagine finding rocks in that colour, are inorganic colours. Rocks are really good at being opaque, but even better at being old. If you take a coloured opaque rock and pulverize it into a fine powder, the powder will be just as opaque as the rock. If you use that coloured powder to tint a paint, then the powdered rock particles in that paint will ensure that it provides relatively good hide.
Also, anything that's 300 million years old HAS TO BE extremely chemically stable. Otherwise it would have decomposed by now. That extreme chemical stability results in rocks being extremely colourfast. A reddish brown or mustard yellow rock can lay for centuries exposed to the Sun on one side, and if you pick it up and turn it over (and clean and dry it) you'll find that the exposed side is exactly the same colour as the underside. That means, even centuries of exposure to the UV light of the Sun isn't enough to fade a rock. So, if you pulverize that rock into a fine powder and use that powder to colour a paint, the paint you get will be equally fade resistant.
So, to get better hide and much better fade resistance, opt for a colour that calls for as much inorganic pigments as possible and as little inorganic pigments as possible.
Also, the flatter the paint, the better it will hide an underlying colour. However, the flatter the paint, the harder it is to clean because of it's rough surface.
Tell your friend to pick out the colours he/she likes the most, and then to see if any of them call for only inorganic pigments in their tint formula.
Would i go about preparing the room by cleaning the walls, lightly sanding them down, then paint over it with an undercoat..wait until its dry and then add the top coat?
Certainly it's a good idea to clean walls before painting them. Be certain to rinse any cleaning solution off the walls, too, and then allow time to dry. You only need to sand the walls down if they're a semi-gloss or gloss if you're painting latex over latex or oil based over oil based. Otherwise, you can just paint over the existing paint. If you want to paint a latex paint over an oil based paint, then you'd need to roughen the existing paint for the top coat to stick well. Rather than sanding, you can roughen the existing paint by cleaning it with a cleaner (like Mr. Clean) and a green 3M Scotchbrite pad (like they sell in grocery stores for scouring pots). The fibers of the Scotchbrite pad are impregnated with a fine abrasive that will abrade the surface of the paint you're cleaning.
Is there a certain type of paint i use for the walls and a certain type i use for the woodwork around the edges?
I own a small apartment block. I like to paint my walls with latex paints and my trim (like door frames and baseboards) with an oil based paint. The reason why is that when I repaint the walls the same colour (after a dozen years or so, I just have to repaint the walls and ceilings, and only clean the oil based paint on the baseboards and door frames. That's cuz tenants will typically put nail holes in walls, but no one puts a nail hole in a baseboard or door frame.
Also, it's common for people to paint the ceilings a much lighter colour (like white) and to use a flat (or flatter) paint on the ceiling. The reason for this is that ceiling mounted light fixtures or windows that come within a few inches of the ceiling can make every imperfection in the ceiling stand out. By using a flat paint on the ceiling, you camoflage those imperfections.