# Communities > Modern-era Swords and Collecting Community > Modern Production Katanas >  Acid etching hamon

## nathanarcher

Hello,
I did a search and have found that the most common etchants were ferric chloride and vinegar mixed with dishwashing soap... heated

Some immerse the blade in the solution, and one person described brushing it on.

However I also found that, especially ferric chloride can leave back oxides and pits etc if left on too long.


My question is,
What are safe time intervals for each etch for both
*vinegar
*ferric chloride

And how much dishwashing soap to etchant ratio/amount to use?

I was planing on brushing it on to give more control.
However, does the etchant change the color of the steel in general, where the harmon is not?
As in... you could see where the etchant was, and was not applied in the finished product, if I opted not to apply the etchant to the shinogi-ji area? Or is this safe to do so or advised against (and should cover the whole blade).

Thanks.

----------

