I am doing some acrylic painting and watched some Bob Ross and he wets his canvas with "liquid white" and then paints on it while it's wet. Is this just acrylic white paint or is it gesso? I have tubes of white paint but it is so thick, it definitely is not liquid.
It's a proprietary product from the Bob Ross company.
There's 3 such basecoats that the company makes: Liquid White, Liquid Black, Liquid clear.
The official description reads:
Liquid White is one of three Bob Ross Liquid Basecoats essential to the Bob Ross Wet-on-Wet Technique®. These basecoats (Liquid White/Black/Clear) allow us to actually blend and mix colors right on the canvas rather than working ourselves to death on the palette. The Liquid White/Black/Clear can also be used to thin other colors for application over thicker paints. The idea that a thin paint will stick to a thick paint is the basis for this entire technique.
Bob Ross's mentor, Bill Alexander, used a similar wet-on-wet technique using "magic white" as a base, or sometimes called "fluid white".
All you need to do is dilute titanium white with linseed oil. Mix these together until you get a creamy consistency. Some artists choose to mix equal parts of linseed oil and Turpenoid (or turpentine) to create this homemade medium.
So, linseed oil and titanium white (paint). I would presume that the quality of the titanium white paint you use will affect the quality of the fluid white you make.
Since oil paint itself is generally made from linseed oil, pigment, and a binder/emulsifier to get the oil and pigment to "stick", it's likely feasible to make liquid white using pure pigment (titanium dioxide), linseed oil and something like white beeswax.
If you are using acrylics and not oils you could make something similar by thinning the base white with some gloss or semi-gloss medium and adding retarder. You can adjust the liquidity with water.
The retarder would be key since the idea is to keep the ground wet while painting to be able to do the special Bob Ross techniques. It will probably be needed to be mixed in with all the paints. But I think Bob's method really calls for using oils. You will have a much harder time with acrylics since they dry so much faster.