A question about Pumice

[Davkin]

First, I did a search and looked through 5 pages of threads and came to the conclusion that a direct answer to my question if it exists at all could take hours to find so I'm starting yet another thread on the subject.

I am considering making my own ground to apply to mdf panels, but I don't want to spend the crazy money they require for pre-made pastel grounds. I have plenty of gesso, but I need to know what grade of pumice I should get and where I should go looking for it. I'm used to working on Uart 400 and would like to create a surface with similar tooth, a little finer is okay but not much. So, for those who have worked on a coarse sanded paper and a custom pumice ground, which grade of pumice most closely equals the tooth of coarse sanded paper? Second question, where am I most likely going to be able to find that grade of pumice locally and online?

Thanks

David

[SSB]

Alan Flattmann says he uses FF grade. He knows a thing or two that man does. He said he loved Ersta, which IS UART now I hear, so it ought to work for you. Let me know please, I have only used the pre made ground in a jar.

[westcoast_Mike]

Woodworkers Supply carries it (woodworker.com). They carry FF (coarse) and FFFF (fine). It will run you about $9.00.

[Davkin]

Thanks guys, looks like FF is what I need. How much area do you think a pound of pumice will cover? I'm sure a lot more than I can use up any time soon but I want to have a general idea.

David

[Davkin]

Okay, I've answered my own question. I found a local source for the pumice. I made a mixture of 1/2 cup each of the pumice, gesso and water. I used a small, fine foam roller to apply two coats and I figure I covered nearly 18 sq. ft. Good thing I had plenty of panels already prepared. I did a little test on one and I can't say it's like using Uart 400. The big issue I see is the roller left a texture that's hard to fill. I'll give it a good try though, but I have doubts this will replace Uart paper for me.

David

[murphe]

Maybe a bit too much pumice? Perhaps if you used less the roller marks wouldn't be so obvious and you could just do more coats?
Either that or put it on with a brush and make the textured marks a feature?
I seem to remember I used less than that and just had to rub down a few high spots with my fingers - which are probably as tough as some sandpaper anyway.
My pumice is the finer grade as well so maybe that helps with the application marks. My only problem is I bought some cheaper watercolour paper with a lower cotton content to apply it to and I can't get it flat after application.

[sketchZ1ol]

hello

- from the Content Area , Article Index under ' Pastel ' ;

http://www.wetcanvas.com/Articles2/47843/575/

Ed :}

[Colorix]

I found that foam rolling it on created way more texture than brushing 3 thin layers (letting dry between). On the other hand, maybe a thinner (more water to the gesso) mixture would not retain the structure as well.

[Davkin]

The next step is to try a foam brush, light layers might work. I don't want brush marks, that's why I used the roller. The roller works great for oil painting panels but apparently the texture it leaves is a little much for pastels. I feel like it's the gesso holding the pastel more than the pumice.

David

[Colorix]

David, I brushed with a regular paint brush (synthetic, smooth finish for cupboards and the like that needs a high shine), and changed direction of strokes for each layer. Worked beautifully to an even surface. I think that gesso/grit mixture was watered with at least 25% more water than the rolled on mix.

[T Porter]

Hi David

I’ve been experimenting with creating my own ground too and here is what I have had success with so far.

1 cup of gesso
1 cup of water
3 tablespoons of pumice
acrylic paint as desired (for coloring)

The grade of pumice that I have been using is FFFF. After mixing the ingredients listed above use a small foam paint roller to apply the ground. Then while the applied ground is still wet, but starting to get somewhat dry lightly dry brush the whole surface to work out the roughened surface that the foam roller leaves behind. If needed, apply a second and third coat and follow the rolling on and dry brushing steps that were used in the first coat. Once the ground has had a chance to thoroughly dry lightly stand the surface with 600 grit sandpaper until the surface meets your approval. These steps have produced a smooth surface with plenty of tooth for pastels.

I ordered the pumice from Covington Engineering http://www.covington-engineering.com...ng_Powders.htm For a break down of grit sizes, here is a chart to refer to. http://www.reade.com/Sieve/grit_conversion.html For a visual of pumice sizes, here is a link that shows different grades of pumice. http://www.kramerindustriesonline.co...comparison.htm

Dakota Pastels also sells 4F pumice 2# for $5 http://www.dakotapastels.com/pages/p...rsgrounds.aspx and if you want a really coarse ground you might want to check out Aluminum Oxide. Harbor Freight sells 2# of 220 grit Aluminum Oxide for $10. http://www.harborfreight.com/catalog...aluminum+oxide

Good luck!
Tom

[Dcam]

David, I like to start with a paper that has some tooth ; live Reeves printmaking paper or a cold pressed watercolor paper mounted on board, and since I like to use pan pastels before the sticks ( a very rough pumiced texture can eat up pan tools), I mix MARBLE DUST with my gesso and get a surface that has good tooth but not like sandpaper. I get my marble dust at Jerry's Artarama". There are times when I want a little more tooth and mix marble dust and FF pumice. I get the pumice at an old hardware store in my area. The famous "Daniel Greene" often uses powdered quartz for his mix. Google his work sometime .

Good luck buddy.
Derek