There are no set rules for scrimshaw...despite what some may say.
I was a professional scrimshaw artist for a bit over 10 years. It was how I made my living and it was during the "heyday" of scrimshaw. I worked in Westport MA, a few minutes from New Bedford MA arguably the "home" of scrimshaw as it was a home port for the whaling fleets on the East Coast.
The whalers used whatever they had on hand to while away the boredom of sitting on a ship in the middle of the ocean waiting for the whales to appear. They used needles, awls, etc. to engrave the teeth of the sperm whale. Many of the engravings are very crude...seen at the New Bedford Whaling Museum...though some are truly beautiful works of art. Lamp black, etc. were some of the materials used to fill in the engraved lines bringing the work to life.
I used "Higgins" black for the line work. I don't remember the brand of ink I used for colors but it was adequate but not great and tended to fade if worn every day as the sun fades pretty much everything over time. We also preferred to use Krylon sealer as the best sealer as it remained clear and did not yellow with time as others sealers we tried did over time.
The key is to start with a very well sanded and polished surface.
Here is a quick run down on how I created a piece.
Starting with a flat blank I mounted it on a small piece of sheet plastic, 2" by 2", using double sided masking tape. This gave me a stable mounting surface that would not move during the engraving. Next would be to coat the surface with a nice layer of Higgins black ink and allow it to dry for a few minutes...do not allow the ink to remain on the surface for hours or days as it becomes harder to remove at the end of the engraving. Begin engraving. I did it all freehand but sometimes I'd use a very sharp pencil to give me a basic outline if it was something new I was working on. The lines appear white as you engrave through the ink and polished layer of ivory or whale tooth blank. Once finished I dip a cotton swab into the bottle of Higgins black and swirl it on the blank to completely fill in the engraved lines.
Everybody in the biz at the time had their own methods for ink removal and some were kept secret though really there are no special ways only what works well for you. For me I used small pieces of cardboard folded over. I would lightly sand a folded corner, with fine sandpaper, until I had a nice flat surface. I'd use this surface to scrub off the ink coating, sanding the ink build up off the cardboard as needed. I then take a bit of paper towel folded in half and covering my index finger...tap it on a damp sponge to dampen it and gently wipe away the residue on the surface leaving the engraved lines a nice deep black.
If if was a color piece I'd then paint it with the inks needed and allow it to dry for several hours or more as needed. The best way to coat it with Krylon, that I decided on, was to spray some Krylon into an empty baby food jar and dip a bit of paper towel into the liquid and gently coat the surface and allow to dry. Spraying it left a dimpled effect I did not like. Krylon dried clear and did not add to or subtract from the work.
I did this every day for over ten years until the ban on elephant ivory and whale teeth was introduced and killed the market...though truth be told there was such a market saturation of "scrimshaw" and especially fake scrimshaw on plastic, etc. that the market was already dying.
Here are some pics of my collection: I don't have much if any "traditional" work as I did so much of it I was bored by it and preferred doing other, more interesting pieces for myself...I started selling my work in '73 and worked at it until '85 ish.
http://s83.photobucket.com/user/Kai_Winters/slideshow/Scrimshaw
This was my first tooth and though crude in the photo looks better "in hand".
Western theme request.
Traditional "Henry P Morgan" ship.