Here how I do/did it. I wear rubber gloves and goggles. I get a clean qt. mason jar, I have a 250 ml glass beaker I use for measuring ( a four ounce straight sided glass would work), I have used iron filing from a school science supply shop, of course the nitric acid and distilled water(have used rain water. I also bought some foot long glass rods for stirring from the same science supply store. I have also used several small chunks of wrought iron, say small 3/8" square. Make 4-5 probably don't need them all but you might. I got my nitric acid from Antec in Louisville, KY. I get a 5 gallon bucket and fill it 3/4 full of plain water. Have a garden water hose handy.
do this outside preferably when the wind is blowing away from you or anything else you don't want to be down wind from the fumes.
I measure out 750 ml of water and put it in the mason jar. I dry out the beaker and pour 125 ml of nitric acid into the beaker and then pour that into the mason jar. Put the beaker into the bucket of water. I use a glass rod to carefully stir the acid mixture and then carefully put it into the bucket of water. I take the iron filings or other iron and drop them into the acid mixture. They will form bubbles on their sides and slowly start to react. I start out slow, no need to rush things, maybe two or three of the chunks. The iron filings will react faster and more violently, I put in a teaspoon at first and let that calm down. Some people use steel wool which can go nuts fast in addition to introducing who know what other metal. When the iron filing calm down and are no longer producing red fumes(do not go near the red fumes) I add another teaspoon of filings.
The next day I check to see if any of the metal remains. Can pretty much guarantee the iron filings will be gone so add some more and expect some more action. Write down how much you add for the next time. If using the iron chunks you stand a good chance that there is still a little bit left. I usually add one or two more especially if there is a lot of action remaining. You basically keep adding iron until any sign of reaction stops. I will add one last chunk or one last teaspoon of filings just to be sure. I like to take several days with this. After the reaction stops, I pour it off into small brown glass jars with tight screw top plastic lids but I don't tighten them up yet. Give them about a week and then tighten and store.
Some keep the sludge in the bottom. I pour that off and discard.
Wash the glass measuring beaker or whatever and the glass rod after using. If by chance you spill the acid on you or your hands use the water bucket immediately and worry about cleaning the beaker later. Do this outside and have the hose ready in case of spills.
I do a 1:6 acid to water. Always add acid to water not the other way around or you will get to use the water bucket and the hose and probably go to the emergency room. Acid to water as a fellow oughter.
Be very careful with the acid. You will probably have to buy a liter and that will make a lot of stain, 8-9 batches. The glass liter bottle wil come with a bakelite lid that is supposed to be acid resistant. My last bottle of acid lasted two years and would still be there but the acid fumes ate the bakelite lid and an open bottle of nitric acid is not desirable. I made one last batch, cleaned everything up and disposed of the bottle. Now I no longer have to worry about having nitric acid around.
Again be careful and have a plan in case you spill.
