The same result may be obtained by the use of megilp, a mixture employed by artists.    From Wordnik.com.  [The Detection of Forgery A Practical Handbook for the Use of Bankers, Solicitors, Magistrates' Clerks, and All Handling Suspected Documents] Reference

As long as a painter is a painter merely, he should not be allowed to talk of anything but mediums and megilp, and on those subjects should be compelled to hold his tongue; it is only when he becomes an artist that the secret laws of artistic creation are revealed to him.    From Wordnik.com.  [Miscellanies] Reference

Van Eyck's manner) and those painted with oil alone, or with the modern megilp, (oil and mastic varnish,) is so well known that it is scarcely necessary to allude to it.    From Wordnik.com.  [Blackwood's Edinburgh Magazine, Volume 57, No. 357, June, 1845] Reference