Veritas Purple Indelible Pencil #83U0116. 12 Count

These extra-hard indelible pencils leave a distinct, long-lasting mark. It is often helpful to wet the surface first with a spray-mist bottle. Suitable for use in scribers, they mark with very little pressure, allowing you to concentrate on accuracy.
All smear with a wet finger. All write much more boldly on a slightly damp surface, and all leave a mark with more contrast after erasure if the surface is slightly damp when first written upon. Don

Since indelible leads react with moisture, it is best to store indelible pencils in a dry place (e.g., Zip-Lock bag) so that the leads do not absorb moisure, causing them to become soft and to wear more quickly.