Machinist blue layout fluid - video

[mwmkravchenko]

I usually use a black marking pen for layout. I don’t think it the safest practice to be mixing volatile chemicals in the home shop.
For scraping of precision surfaces I like Prussian Blue.

He's using ethanol. One of the safest thinners out there.
If you use WD40 you are using a more dangerous mix of acetone and cooking oil. Acetone like alcohol is easily absorbed through our skin. Acetone however is known to cause cancer if used without proper precautions.