Yet another etching question

[CodeMonk]

For the last few years, the Muratic acid I have been using had a Hydrochloric Acid content of 14.5% (Usually bought at Home Depot)
Today I bought some that had a content of 30% (Its all they had at Lowes hardware)
With the the 14.5% stuff I used a mixture of 3/2 of Muratic Acid/Hydrogen Peroxide, which worked pretty well for me.

Since my copper blank supply is limited ATM, I don't want to waste any of it.
So will I need to change the ratio?
If so, suggested ratios?

Thanks.

[Pettol]

I haven't tried that mix, but I think I should.
If you have been successful with your recipe, why change it? So I would first dilute the acid with water 1:1 and then continue as before.
But remember, ALWAYS add the acid to the water (careful there)! NEVER the other way around!

[CodeMonk]

I was just wondering since the HCL content is twice what I have been using.
I do have some small scrap pieces I guess I can test on. big enough to make a Bazz Fuss on anyway

Thanks.

[jogina111]

if previously, you're using 1:1, then you can double the ratio of the hydrogen peroxide...like 2parts of Hydro peroxide to 1 part of muriatic acid..will result the same as your former solution

[Pettol]

It'll probably work either way, but:

if previously, you're using 1:1, then you can double the ratio of the hydrogen peroxide...like 2parts of Hydro peroxide to 1 part of muriatic acid..will result the same as your former solution

No. That would give a higher hydroperoxide content. That's why I suggested diluting the acid first.

[PRR]

> double the ratio of the hydrogen peroxide

It is a THREE-part problem. Acid, peroxide, and WATER.

Lowes sold him some stuff that's short on water.

What Pettol said. Slowly dribble a pint of 30% acid into a pint of cold water to make 15% acid. (15%, 14.5%, probably no difference--- anyway that "30%" might be 28% or 31%, it's only for cleaning concrete.) Then use your known-good recipe.

[Keppy]

Pettol and PRR are right that you need to dilute the acid with water to get the solution you're used to, but there are plenty of other ways to etch with acid & peroxide.

I've used 30% Muriatic + peroxide in a 1:2 ratio many times. 1:1 works too, and after all the peroxide reduces to water & oxygen you're left with 15% acid, to which you can add peroxide and etch again.

I personally would not add water. This reaction relies on the oxygen that is produced as the peroxide reduces, so adding more peroxide instead of adding plain water will give you more activity in your batch of etchant. The best reason I can see for diluting the acid with plain water is if you have refined your process to very specific etching times, which seems unlikely given that peroxide loses it's strength over time, even while still in the bottle, and so tends to give varying results.

Any of the recipes mentioned so far in this thread will work just fine.