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Why are sharpie pens acid resistance?

What's the chemical compound of the sharpie to make it acid resistance? Such as for PCB etching.

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In the case of using a copper clad board without any photo resist... Permanant Markers use water resistant chemicals like Permachrome, xylene and toluene. It's these chemicals that prevent the acid from penetrating to the copper layer. Permachrome if also found in some ink-jet inks. Xylene is a clear solvent used in paints and varnishes, and toluene is typically found in crude oil and gasoline.

nfarrow (author)  mpilchfamily1 year ago

Do you think Permachrome would work with Cyanotype?

nfarrow (author)  nfarrow1 year ago

Potassium ferricyanide and Ferric ammonium citrate


iceng nfarrow1 year ago

Us a cardboard shape on a hankie and put it in bright sun light or UV for a couple of hours then rinse the Potassium ferrocyanide and you will have a lovely blue print.

No Idea.

rickharris1 year ago

It isn't PCB etching is done on a photo resist layer, You mark this with a dense marker such as a sharpie. The photo resist is then developed under IR light this makes the exposed parts soft they can then be dissolved in the developer leaving bare copper everywhere except for the black lines and dots.

You remove the bare copper with some kind of etchant to leave the tracks.

The photo resist is acid resistant not the Sharpie.

nfarrow (author)  rickharris1 year ago

A black Sharpie is acid resistant.

rickharris1 year ago

I have never tried to make a PCB using bare copper board and a water proof marker have you?

I would expect the etchant to creep under the tracks as the line made by the waterproof market will be very thin.

I could be wrong of course , often am!

nfarrow (author)  rickharris1 year ago

https://www.instructables.com/id/Making-a-Hand-Drawn-PCB./

Why not ask the manufacturer?
Those are so called "trade secrets" and I doubt you will get the answer you seek.
Sharpie or not, the only thing that counts is that the area covered is not affected by acid.
Most spray paints do this too, so it is not a matter of chemicals but particles.
Any marker pen uses a solvent with the "paint" dissolved in, once dried only the pigments and binder are left.
As those pens are quite cheap I would not bother too much about ingredients and just buy a new one.