Potassium Nitrate Home Production

Potassium Nitrate, also called saltpeter, is a wonderful compound with a multitude of properties. Potassium nitrate can be used for numerous things including fertilizer, fireworks, gunpowder, seasoning, and even removing stumps.

I am primarily interested in using it as a fertilizer since I am quite fond of my plants, however I might make a small sugar and saltpeter firework display later this year for fun.

To make this compound, we are going to rely on materials most of us have on hand. This will allow you to have a practically endless and free supply of the stuff.

The general idea is to make compost. Compost is loaded with nitrates depending on the ingredients and drainage. Since nitrates are quite soluble in water, we need to either lay down a tarp or find a container (trash bag, bucket, etc.). In the container or tarp, add hay, straw, leaves, etc. These are low in nitrates but are needed for the compost. To add a source of nitrogen, urine or bird manure works well. Other mammal manures can work, but since birds mix their "urine" with their feces, bird manure is much greater in nitrogen content. Feel free to add as much of these ingredients as you want. Keep in mind that oxygen needs to get to the bacteria so drenching the material in liquid will not work well.

After allowing the material to decompose for several months, submerge the compost in a bucket of water. This water will extract the nitrates from the compost. After soaking, run this mixture though a strainer to remove all the debris. The debris can be used for plants or for more compost.

The left over liquid contains various carbonates. One of the common ones is calcium nitrate. This can be removed and converted to potassium nitrate by adding potassium carbonate. To find a free source of this, look for wood ash. According to Cody's Lab on YouTube, hardwood ashes work best so you have less sodium carbonate present. Mix this ash into the bucket for a few minutes and let sit.

Since calcium carbonate is mostly insoluble in water, our bucket can be filtered to remove practically all of the calcium. The left over slurry can be rinsed with a little water and filtered to improve yield. Keep in mind that this can also increase impurities in our final product. Allow this water to evaporate.

After evaporation, the salts present should be a mixture of potassium and sodium nitrate with a few impurities. Since potassium nitrate is about 14 times as soluble as sodium nitrate (according to Wikipedia) at 100C, a hot filtration can be used. To do this, add the dried salt to a small amount of boiling water. How much to use will be completely dependent on your quantity but needs to be as minimal as possible. There should be some salt left undissolved, but the dissolved salt should almost entirely be potassium nitrate. While still close to boiling, pour this solution through a filter.

Now that there is dissolved potassium nitrate, allow for the temperature to fall to room temperature followed by placing the solution in an ice bath. This should form nice, large, mostly pure crystals of potassium nitrate. If no crystals appear, drop a piece of salt, shake the container, or tap the inside with a stir rod to cause the salt to crash out of solution. This works because potassium nitrate is 18.5 times more soluble at 100C than 0C. If the correct amount of water was used, you should see crystals. This can be filtered to obtain the potassium nitrate. Allow to dry.

If no crystals form after the previous steps, too much water was added or your yield is extremely low. Allow the water to evaporate to reclaim your salt. Note that you can boil away most of the water but this can only be done under watchful eyes. If all the water is boiled away, the temperature can skyrocket. This will either shatter your container, cause explosive decomposition of the potassium nitrate, or both.

Best wishes for all of you. Let me know how it goes and if you have any questions.

PS: According to a few sites online, if you live in the US, you can store up to 50 pounds of black powder. You can use it on your property but selling it is completely illegal. This can differ from state to state or from town to town. Do your own research on this. I am not liable for any decisions you make based off this article. My sole purpose here was to show how to make the potassium nitrate since it has many uses.