DIY : Alternative Engineer’s Blue — A DIY Solution – The Rebuild – Medium

Some of you, especially some machinists, will find the title a bit ambiguous due to the use of “Engineer’s Blue”. Engineer’s Blue usually refers to the colored paste used when mating two components, however, it is sometimes also used to describe “Marking Blue” or “Dykem” (Named after a popular brand).

Now, what we’re taking a look at here is both! I’ll split the article into 3 parts:

  • Prelude (You’re reading it now)
  • Marking Blue (For marking, duh…)
  • Engineer’s Blue (For scraping)

Marking Blue

This stuff is amazing!

Wikipedia describes Marking Blue as

… a dye used in metalworking to aid in marking out rough parts for further machining.

It is often refered to as “Dykem” and it, usually, has a blue color. However, some manufacturers also provide it in a red color.

To use it, you simply apply it to a surface and once it’s dried (It’s fast drying, usually within minutes) you’re free to “draw” your layout or markings using a scriber. The blue color creates a contrast to the scribed line, which will be the color of your materials surface. There’s not much more to it.

The color used in Marking Blue is traditionally Prussian Blue, however I’ve also seen Crystal/Gentian Violet used. I’m not entirely sure why one is preferred above the other, but I suspect that the fact Crystal Violet is a liquid and Prussian Blue is a pigment can have something to do with it. If the pigment isn’t of sufficient quality, it would need to be grounded/sheared (using something like a 3-roller mill) for it to be completely dissolved or dispersed. Atleast, this is true for making paint (and Marking Blue is essentially a dye).


Some of the recipes that I’ve seen, and that I’d like to eventually test and write about, is listed below.

The most basic recipe

  1. Denatured Alchohol
  2. Prussian Blue


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