Cleaning the slide calculator
From the manufacturer:
In regards to cleaning varnish coated items, I would recommend using a "Lysol" or equivalent disinfectant wipe. Use very light rubbing pressure followed with a quick buff dry. This can remove the varnish or ink if applied too frequently or if applied in excess.
Any solvent based cleaner will attack the varnish.
DO NOT USE AN ALCOHOL BASED CLEANER ON THE CALCULATOR.