Marking out a metal bar Marking blue or layout stain (sometimes called ''Dykem'' after

trademark erosion A generic trademark, also known as a genericized trademark or proprietary eponym, is a trademark or brand name that, because of its popularity or significance, has become the generic term for, or synonymous with, a general class of Good (econom ...

of a popular brand, or ''

Prussian blue Prussian blue (also known as Berlin blue, Brandenburg blue or, in painting, Parisian or Paris blue) is a dark blue pigment produced by oxidation of ferrous ferrocyanide salts. It has the chemical formula Fe CN)">Cyanide.html" ;"title="e(Cyanid ...

'' after the blue pigment) is a

dye A dye is a colored substance that chemically bonds to the substrate to which it is being applied. This distinguishes dyes from pigments which do not chemically bind to the material they color. Dye is generally applied in an aqueous solution an ...

used in metalworking to aid in marking out rough parts for further machining. It is used to stain or paint a metal object with a very thin layer of dye that can be scratched off using a scriber or other sharp instrument to reveal a bright, yet very narrow line in the metal underneath. The advantages are that any existing scratches are covered with the dye and the new lines have a contrasting background. Prussian blue and Dykem or layout fluid are not the same. Prussian blue is non drying and used to mark place of pressure contact between two surfaces. Prussian blue is transferred to the surface. Dykem, layout fluid dries and is mostly used to provide bright lines when using a scribe to mark hard surfaces or point of contact between two surfaces. Dyken is removed from the surface.

Composition

Marking blue is made by mixing methylated spirits with shellac and gentian violet..

Alternatives

felt tip marker A marker pen, fine liner, marking pen, felt-tip pen, felt pen, flow marker, sign pen (in South Korea), vivid (in New Zealand), texta (in Australia), sketch pen (in South Asia) or koki (in South Africa), is a pen which has its own ink source ...

can be used as they are convenient and tend not to dry up as quickly. On rough structures, such as castings or

forging Forging is a manufacturing process involving the shaping of metal using localized compressive forces. The blows are delivered with a hammer (often a power hammer) or a die. Forging is often classified according to the temperature at which i ...

s, whitewash or a mixture of chalk and water can be used. A solution of copper sulfate, distilled water, and a few drops of

sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular formu ...

can be used on machined surfaces.

Safety

Marking blue is considered non-toxic. If heated above 250 degrees Celsius it will give off toxic Cyanogen gas. Metal cutting commonly heats material above this level.

References

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