Anyone know what episode(s) Bob introduces Liquid Clear and Black Gesso?

Can't help you with the exact episodes, but I think it's the Liquid Clear reacting with Paint Thinner, that you're thinking about. He shows in a few episodes 'spraying' paint thinner on a liquid clear canvas creates a neat 'bubble-dotting' effect.

Try the color search on http://www.twoinchbrush.com

first black canvas was series 1 ep 3.

liquid clear i think is season 9 ep 2 (a seascape)

for black canvas Bob refers to acrylic paint from the start of season 1; which is in fact all that Gesso is; liquid acrylic. i think Season 10 was when he first starts to refer to a black gesso for black canvas'

as for advice:

• item 1: Gesso; dont be fooled into buying Bob Ross Gesso. ANY acrylic paint will suffice! buy the cheapest stuff you can! If you get it then buy a liquid acrylic out of a bottle! its far easier to apply and cheaper by far. Apply the acrylic with a craft roller! or a sponge roller. if you have to then use a sponger applicator brush...and finally use a standard brush (not one you will oil paint with) as a last resort! If you apply using a brush them chances are you will use far far more paint than you need and end up with a more textured canvas showing brush strokes than one showing the texture of the canvas itself. its also takes ages to paint it on. Do yourself a favour a buy a cheap craft sponger roller!

• item 2: Liquid clear: apply less of this than you would liquid white.; a little goes a very long way. on a black canvas its really easy to see where you have covered because the liquid clear will make things shiny. put a little on one corner first then scrub it outwards, then apply more if required. think roughly half the amount of liquid of white you would use. liquid clear has a violent reaction with thinners (its used to effect in several episodes), so always make sure you are painting with a very dry brush.

Any advice would definitely be welcome as well.