DRY CONCENTRATED ETCHANT

This stuff really gets warm (actually hot) fast when being mixed. Mix into the water SLOWLY. Etches just fine.

http://www.electricstuff.co.uk/pcbs.html states that if a new batch of anhydrous FeCl3 solution doesn't etch, you can add a touch of hydrochloric acid to "kick" it into gear. This allows much more FeCl3 to dissolve into the solution as FeCl3 is not very water-soluable at PH 7.0. Alternatively, putting a clear bottle of new etchant in the sun for a few hours should accomplish the same thing - FeCl3 solution is photochemically reactive, so otherwise keep it out of sunlight. And by the way it is the FeCl3 that etches boards, not the HCl. HCl only allows more etchant into the solution.

It might be argued that other etchants such as ammonium persulphate and copper chloride are better, but FeCl3 is cheap and effective, so it gets 4 stars. However, please consider the disposal of this stuff. Do not pour FeCl down the drain! It will eat your sink and pipes (including iron and stainless steel) and it badly pollutes the environment. Instead, a nice disposal method is to slowly add either 0.5 parts sodium hydroxide (for the insane among us) or an equal part sodium carbonate or 1.5 parts sodium bicarbonate (baking soda.) This renders the stuff inert. When mixing acids and bases, always add the solids to the liquids, slowly, while stirring. And of course, be careful with any highly corrosive chemicals.

this is good stuff if you are on a shoe string budget. otherwise i dont think it is worth the hassle. the powerdery stuff to make the etchant can get all over the place and stains really dark spots whereever it hits. you will want to be very careful and read the instructions too. you have to poor the powder stuff into cold water, not the other way around or it will have a concentrated reaction and might melt your container or splatter all over.
overall its not a bad deal, you would spend a lot more for normal etchant.