What to use as the background for a self-made scratchboard (or scrapeboard)? What is this about?

I wish to make a scratchboard or scapeboard myself:


Scratchboard definition on Wikipedia.  
More information here




My Problem

Take a look at this video from David Rooney. He is an illustrator and I would like to build my own scraper board as he does. The problem is that he does not explain how to build the white background board. He says that is a chalk-covered board, but I cannot find it in any shop and I don’t know how to build it. Some websites say that they use a clay board.

My questions thus are:


What kind of board should I should use?
How can I find it?


What I tried so far

I found this scratchboard recipe. Basically the steps are:


Combine 3 parts of glue, 1 part of water and 1 part of plaster.
Apply a thin layer to the wood coat.
Apply a thick layer going in one direction and wait about 10 minutes to dry.
Apply another thick layer going the other way and let sit to dry completely for 4–8 hours.
Sand down the plaster until smooth, using a medium-grit sandpaper.
Mix together 3 parts black acrylic paint and 1 part dishsoap.
Apply paint/soap mixture using a foam roll brush or just a foam brush. You can use black ink instead but the paint mixture seems to scrape off the easiest.
Let dry for 8–24 hours before trying to scratch.


Note 1: You can use black ink instead but the paint mixture seems to scrape off the easiest. I think David uses oil ink (indian ink).

Note 2: I have tried with normal plaster but the color was not completely white. So next time I am going to try adding zinq oxide to the mixture. It is a white pigment to make it less transparent.
What you are looking for, the base for a scratchboard, is Clayboard. It is available in art stores and online... search for art panels.  

You can make clayboard a number of ways:


The Jimmy Arborough site has a recipe for rabbit skin glue based
ground. Rabbit skin glue is tricky in that it requires hot water, cooling time, and is made out of rabbits. He uses about a 1:1 ratio of water to clay in his recipe. 
The white glue and plaster method is popular and easy. Use plaster of paris not drywall compound to get a brighter white. 
You could also mix kaolin clay or plaster of paris with regular acrylic ground and apply that.  Here start with 1/3:1 ratio of clay to base, adding more clay to get the absorbency/feel you desire.


With any of these methods you can whiten the base by adding Titanium White. 

Once you have a ground, apply it in multiple layers to masonite or heavy paper board in layers, letting each layer dry between applications. You will need a number of layers (5-10) to get the right thickness. If the board warps, try painting the back with an X of the same ground to pull it back into shape. When the board has dried thoroughly, lightly scrape the surface with a knife to remove any blobs or burrs, then sand smooth with a fine grit sandpaper.  

To finish the scratchboard, take a dry and clean clayboard, brush or spray with India Ink, again layering until you have the tone you want. The result should be a smooth hard surface, ready for carving into.