Post by koolbraider on Jul 7, 2012 14:18:29 GMT -6
In my never ending quest to find what the heck is happening to my copper blanks I noticed that my etch, peroxide and muriatic acid, was getting rather hot. I don't remember this ever happening. I'm sure it didn't happen last year since I was using a double sized batch and the container never felt this way. This ever happen to anyone else?
When I was a youngster, I used to etch printed circuit boards at home using the etchant that they sell at radio shack. Once time, I poured the etchant into an aluminum pie pan (instead of glass or plastic container like you are supposed to). And of course, I did this in my bedroom. So, in goes the etchant and the printed circuit board. Next thing I see bubbling and fumes coming off and I knew that wasn't right. I picked up the pie pan and ran out of my bedroom shouting "Open the door! Open the door". My mom saw me coming and opened the back door. I ran out of the house and tossed the whole shootin' match into the grass.
Here is where it gets to be relevant to your question. As I was running thru the house the pie pan was getting hotter and hotter in my hands. I tossed it when I got to the door because I couldn't hold it any longer. It is a chemical reaction and it can generate heat if it is a strong enough reaction.
To this day that stain is still there at my parents house on the wood floor where I spilled some of the etchant as I started to run.
Post by koolbraider on Jul 15, 2012 10:10:27 GMT -6
Jim, it's great to have you back; you have been sorely missed. I bet your parents never lose an opportunity to remember this to you! I don't ever recall the solution getting hot before. I am using a smaller container. I guess I was wondering if the muriatic acid goes "bad" after a year or so.
Thanks for the welcome back. I've been keeping an eye on the forum since its move, but I've been spending more time with watches than my silversmithing.
Here is what Tim McCreight says about etching in the Complete Metalsmith (Page 88 in my hardcover copy): "By its nature, acid is a tempermental commidity. Up to a point, diluting makes it stronger. In some cases it gets stronger as it asborbs other chemicals, so acid that has been used for a while is better than a fresh mix. Increased temperature will accelerate the action of acid but once it gets going it produces its own heat and so will continue a strong bite. The only rule is that there are no rules and each time you etch you must pay attention to what is happening."
That kind of sounds like old acid could infact be getting warmer than new acid as it could be stronger to me. And if you ever have to dilute acid, remember the high school chemistry class rule "Do as you oughta, add acid to water". If you add water to acid, it get exothermic and gives off heat.
Post by koolbraider on Jul 16, 2012 9:29:35 GMT -6
Jim, I'm probably having a dumb day but I don't think this is my situation (it might, just am having one of those days). I make a fresh batch of etch each time with the gallon jug of muriatic acid that was new last year. The batches are small but I do quite a bit of work in the summer. In your experience does muriatic acid go bad? I'll try Googling but sometimes it takes a while to get the right words for the search. I like the reminder of how to dilute acid by the way. Tried it the other way around once; things really got popping!