Reconstituting powdered Ferric Chloride

M

mgysgthath

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Dec 15, 2009
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I've looked through the forum and some googling.. no definitive results. I found one post on some UK forum that was such bad grammar (ironic) I couldn't make out what he meant.

Looking to get just a 4:1 basic ratio everyone uses, distilled water of course. Has anyone used powdered Ferric?

Also does anyone know if Ferric Chloride -Hexahydrate is different than regular Ferric Chloride or won't work? It's all I could find at the time.. now I know (thanks to this forum) MG sells it in Canada and can get liquid if you think it's not worth the bother of reconstituting. It apparently releases hydrochloric acid/fumes as it's reconstituting, which means I should do it outside I think.

Thanks all :)
 
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I started using the powdered stuff a few years ago, and i have found that 1 lb per gallon of distilled water gives me a good solution for etching, it seems pretty close to the 4:1 ratio I used with the radio shack liquid. Please do this outside, although I have rarely had it fume, it is a good precaution. I would also advise you start with very cold water, and maybe some distilled water ice close at hand. Mixing the dry powder with water produces quite a bit of heat. I like to mix up a new batch with my mixing container in a snowbank. Putting 1 lb in a gallon of water is almost enough to boil the water if you start at room temp. It is important to stir the mix, clumps at the bottom can melt plastic. I usually add a bit and then stir. I also like to let the mix sit for a day or two before using. This mix works great. I have mixed up about 7 gallons this way.
Thanks,
Del
 
Here is an older post I made on the subject:

FC should be mixed to make a 42 Baume stock solution. You add one pound of crystals to 18 ounces of water to get this strength - one pound to one quart is close enough. Let it sit for a couple days, as Del suggested. Dilute the working solution from this stock . Three parts water to one part stock is what I use ( that is the same as Del's one pound to one gallon).
If you are just making up one gallon, skip the stock solution. If making up a larger batch, one gallon of stock solution is easier to store than four gallons of working solution.

Mix outdoors and don't breath the fumes when it is dissolving. Wearing gloves and a face shield, is a good practice.
 
I mixed 1 pound to 1 gallon and the solution seems like it might be a bit potent yet. I'm wondering if that is more of a "stock" solution or the post-diluted 3:1 or 4:1 solution? Or perhaps the ferric I got is more potent? It wasn't a powdered form after all when I opened it up, but little corn-puff looking balls that took a long time to dissolve. This image is from about 10-15 seconds in the etchant at cooler than room temperature.

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Looks fine from here.
You can always dilute it to lower concentration if you want, but 4:1 seems like the standard. You will find that the contrast in colors will show up almost instantly, but that the darker areas won't etch down much below the brighter areas for several minutes.

After rubbing down the blade with 0000 steel wool or 2500 grit paper, the etching will look a lot less bold. I find that many 1-5 minute etches are better than one long etch. I clean and rub down the blade each time. After the last etch, I often boil the blade for fifteen minutes and then dry while hot. Then it is oiled immediately ( unless the blade is being blued or parkerized) .
 
Thanks Stacy. I like the boldness but I don't like the green tinge, I'm hoping that goes away after scrubbing it. I didn't have any steel wool at the time but I got some lastnight, so once I get it finished and am ready to etch again I'll try your multiple dip method.
Do you boil the blade to neutralize the acid? I was thinking of doing that with some baking soda in the water. This time I just washed it thoroughly with dish soap an warm water, dried and oiled.
 
The FC is neutralized best with ammonia or TSP ( Windex with ammonia is a standard neutralizer ). Baking soda does not work as well as one would think, because the reacting is not just a simple acid etching.

Once you are done etching, neutralize the blade well, and then scrub it clean. Boiling helps remove any salts in the metal pores, and sets the darker color of the etch. Without the boiling step, the dark color can tend to rub off easily.
 
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