Interesting reading as well. I am learning something new every day using my eggbot!
The idea of applying a coating is interesting, I have used eggwhite on wood with very good results – this is a method used by lutherie’s (guitar-builders) – I will try the same on an egg.
Can you share some more info on the “jevel-tip” pens? I reckon making a thin fine hole in a jewel must be a difficult task! I have tried some of the japanese .Too brand coopic pens, Coopic Pens, I am still experimenting with these.
For an explanation on how to derive the correct pen arm height see this link; Eggbot Setup Guide. The post created very little interest (in fact no comments in 1.5 years!) Might be too technical or badly written!