After I posted yesterday, I received an e-mail from Birch with further information on removing yellow quilters chalk.
Here is the e-mail they sent me ...
It is always suggested to test a fabric mark on the same fabric you are using. Fabrics change from supplier to supplier.
Also if the fabric is not pre washed the sizing used in the manufacturing process can sometimes retain some of the colour.
To try and remove markings on your current project first test on a scrap of the same fabric or on an inconspicuous place as it is important that it does not ruin
Some ways to remove chalk from fabric:
1. Brush it with a soft brush – like a soft toothbrush.
2. Gently blot the marks with a soft white cloth and a solution made from ½ white vinegar and ½ water. ( Some quilters use 2/3 white vinegar to 1/3 water). Some people report that that marks don’t seem to disappear until the quilt is dried.
3. Cool water with a drop of dishwashing liquid. Use a soft toothbrush to gently rub the solution by dabbing with a clean sponge and cold water.
4. Use a fabric eraser.
Regards,Birch Haberdashery & Craft
I hope this can help someone else out.