Editing Marking blue

{{short description|Layout stain used in metalworking}}
{{distinguish|engineer's blue}}
{{More citations needed|date=February 2024}}
[[file:Engineers Blue Naomi SexyCyborg Wu 2019.png|thumb|Marking out a metal bar]]

'''Marking blue''' or '''layout stain''' (sometimes called ''Dykem'' after [[trademark erosion]] of a popular brand, or ''[[Prussian blue]]'' after the blue pigment) is a [[dye]] 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.

== Composition ==

Marking blue is made by mixing [[methylated spirit]]s with [[shellac]] and [[gentian violet]].<ref name="brink">{{Citation | last = Brink | first = C. | last2 = McNamara | first2 = B. | title = Engineering Fabrication & Boilermaking | page = 44 | publisher = Pearson South Africa | year = 2008 | url = https://books.google.com/books?id=coOZXYLqqPoC&lpg=PA44 | isbn = 978-1-77025-374-2}}.</ref> <!-- Prussian blue with [[ethanol|alcohol]] to form a quick drying stain.  <-Is this true? -->

== Alternatives ==

A [[felt tip marker]] can be used as they are convenient and tend not to dry up as quickly. On rough structures, such as [[casting]]s or [[forging]]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]] can be used on machined surfaces.<ref name="brink"/>

== References ==

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[[Category:Dyes]]
[[Category:Metalworking measuring instruments]]