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Pictures please. :-D
Just thought I'd share my experience with the following.Mixed 200ml of 30% builders hydrochloric acid with about 70ml of 35% hydrogen peroxide and etched my board. Did not dilute with water. Very fast etching, under 2 minutes, and a nice board. Afterwards the mixture is fizzing and bubbling away like something a mad scientist made in his laboratory. I reckon I could have used much less of both ingredients and reduced the amount of H2O2. If it was way too strong, there were no adverse effects on the etching or the board, and the resist did not get eaten away (pre-sensitised Kinsten board for the UV process).Got the 35% H2O2 from a chemical supplier I found on Google. Have heard mixed stories about the 3% stuff you get out of the supermarket. I tried it a few months ago and nothing happened, but with this 35% stuff, rocket fuel. The supplier gave it to me with the plastic bottle completely wrapped in foil to keep the light off it. He told me to keep it in the fridge too. These two measures he said would make it last a long time. Even if some of it's 35% strength decays, I'll still be left with plenty concentration compared to the 3% stuff.Got to do it outside, preferably with a bit of wind so you aren't getting the fumes up your nose. And don't let the acid fumes get near any metal that you don't want to go rusty. Last but not least, goggles, gloves and a bucket of water just in case you get a splash.I'm going to toss my ammonium persulphate now, I have risen to a new level LOL.