I use sanding blocks–hand sanding–on all my panels, from 4×4 inches, to 4×8 feet.

Yes, the gesso causes little hard, round “pills” to form on the sanding surface, which I can pick off, and continue sanding, I have to watch for them, ’cause (as you noted) if they get large enough, they can gouge the surface,

Still, I usually only have to worry about them on the 150 grit. When I switch to 220, they don’t seem to form…

I know all about sanding gesso . My hardboard panels are sanded level and smooth to remove all brush marks. I start by using a palm sander with either 80 or 120 grit and finish by hand sanding with a block up to 150 – 220.

What will help prevent the sand paper from clogging is the type you use. Not all papers are the same. I like the 3m Sandblaster line. It has a coating on it to prevent it from clogging, plus it lasts longer too. I don’t use anything else.

http://www.amazon.com/3M-SandBlaster-Surfaces-Sandpaper-100-Grit/dp/B000BQN8XY/ref=sr_1_13/180-7064937-3083813?ie=UTF8&qid=1413554613&sr=8-13&keywords=3m+sandpaper

-I begin with lightly scuffed untempered masonite panels from a dude who makes them for me in PA.
-I do 10 coats of Liquitex gesso “surface prep” ( from the little tub with the handle). Each coat dries for a day.
– I sand with a Milwaukee 5″ random orbital sander with 80, then 150 grit disks (but not over-perfect -smooth – from Diablo ( or whomever).. I have never had the issue you are seeing. I live in a dry -ish climate ( Coastal, Northern California) .. I wonder if humidity could effect ? Mine are perfect every time..

Kevin

I opted to purchase a finishing sander. Still had some of the “gumming up” problems, but not as badly because it wasn’t circulating like the orbital sander.

I had a couple of gouge incidents, which I simply used gesso and a putty knife to fix, then sand.

But, at the end I was reminded of the power of a wet rag to smooth it all down and remove the dust

I’m curious, what other forms of gesso are people using? I’ve always used liquitex/acrylic based gesso. In fact, that’s all I find anywhere, even online. Some of the purists complain that gesso is bad for oils, bad for …. so apart from doing my own thing (which I don’t want to do), what options are there?

Thanks.

I use Grumbacher 525 Acrylic Gesso. It has marble dust (calcium carbonate) as one of its ingredients, so it creates a tooth that helps the oil paint to grip it very well. I thin it with water until it is the consistency of cream, and runs (not drips) off the tip of my stirring stick. I apply it with a house, sash brush, and I want it fluid enough to be “self-leveling” as I apply it…….the brush strokes even themselves out shortly after they have been applied.

Actually, I’ve found Liquitex Gesso to be nearly as good as the Grumbacher, but while it is more liquid from its container, I still have to add water to thin it even more for proper brushing. Golden Acrylic Gesso never worked for me; too glossy, shiny, hard, plastic-y, no tooth, does not sand well, at all. I suppose their acrylic paint is wonderful, because that’s rather how their acrylic primer seems to be made. Not appropriate for my use, however.

Some purists may claim that gesso (and by that, I assume they mean, “acrylic primer”) are bad for oils, but I’ve been using it for years, with very good success. What is questionable is painting oils over acrylic paint. Acrylic primer, and acrylic paint are two different things, made of different “stuff”. While I would recommend applying oils over acrylic primer, I never recommend applying oils over acrylic paint.

But some oil painters even believe that to be fine.

In terms of sanding, I guess you are all discussing the sanding of hard, inflexible panels. For canvas, I would never suggest the sanding with either a block, or a rotary sander. Canvas is flexible, and as such, the only areas of a block coming into contact with a canvas would be the corners of the block.

I use 3M Maroon Sandblaster paper, 150 grit, and I sand with my fingers pressing on the back of it so as to conform to the flexibility of the canvas. It has been formulated for sanding latex, and acrylic painted surfaces without clogging. I get about 3 times as much “mileage” with that stuff than with normal sandpaper.

A really good “trick” when sanding a stretched canvas is to place some hard, inflexible piece of cardboard, or sheet metal between the stretcher bar and the fabric during the sanding process. This prevents the occurrence of that little, smooth “line” on the face of the canvas, exactly at the point that the inner edge of the stretcher bar exists. I had that problem for years, until someone suggested that trick, and since then I’ve always used it with very good success. I use a piece of sheet metal smaller than the canvas, tucking in back of the stretcher bar in different places as I sand. I use an old, ferrotype plate from my photography days.:D