Different Etchants

[Kenny]

Can anyone (everyone) who has used these three please coment on the ease of use

Ferric Chloride: apears to be most expensive, dirtyest but sounds like it doesn't need so much aggitation

Ammonium persulfate: cheaper and cleaner but creats O2 bubbles which need aggiation

HCl/Peroxide: I presume asme as above, having great difficulty sourcing Conc HCl

[macfrank]

Can anyone (everyone) who has used these three please coment on the ease of use

Ferric Chloride: apears to be most expensive, dirtyest but sounds like it doesn't need so much aggitation

Ammonium persulfate: cheaper and cleaner but creats O2 bubbles which need aggiation

HCl/Peroxide: I presume asme as above, having great difficulty sourcing Conc HCl

Ferric Chloride is opaque, expensive and needs both heating and agitation. It's also pretty nasty and the stains are difficult if not impossible to remove.

Both Ammonium Persulfate (and Sodium Persulfate) and the HCL/Peroxide mixes are much cheaper, don't stain and are less toxic. You can also get away with minimum agitation and heating with both. Ammonium Persulfate is endothermic when mixed with water (it gets colder, not hotter) so the etching process is helped along if the solution is heated. The persulfates are strong oxidants (even in dry form) so they have some storage hazards.
The HCL/Peroxide mix is exothermic when mixed, but it too likes to be warm.

One way to reduce or eliminate agitation with the Persulfate or HCL/Peroxide etchants is to suspend the parts being etched vertically in a tank, so that the bubbles naturally detatch and float to the top. With the HCL/Peroxide etchant, you can bubble air through an air stone (although it may eventually dissolve in the acid) . Bubbling air through the acid bath has the added advantage of "recharging" the mix somewhat.

The HCL should be easy and cheap to obtain world wide - look for "muratic acid" which is used to adjust the pH in swimming pools.

Frank

[Kenny]

Woops, sure should have spell checkered that first post

Thank's heaps Frank. I had been looking everywhere that I thought would supply chemicals, but never thought of the pool shop. It does seam to be cheapest to go for Hydrochloric acid but is only in large containers that make persulfate better value for my size needs.
I will keep looking and thanks again for pointing me there

[Andrew Gorman]

You should be able to find muriatic acid at the hardware store- it's used for cleaning fireplaces. Strong (30% or so) H2O2 can be found there too as one component of 2-part wood bleach.
Andrew

[Kenny]

I've gone for Ammonium Sulfate,
But it's not working at all.

I am manually aggitating and brushing a test strip of sanded brass but no joy. One small patch has turned a stronger copper color but that is all. The solution is warm but not hot at this stage.

[macfrank]

I've gone for Ammonium Sulfate,
But it's not working at all.

You need Ammonium Persulfate, not Ammonium Sulfate.

Frank