For many years I have done Revolutionary War artillery and I always looked for new information in regards to bettering my knowledge. During this search I have built up a nice display to help educate the public about the many articles of equipment used with artillery.
During these times, I had run across the use of portfires and had wondered how they worked and what these portfires were made of. After months of searching I could not find a formula for them, but I did find a list of some of the elements that were used.
During the winter months I worked on making portfires. With many failures behind me I finally came across the formula for a burn rate of 19 seconds an inch. Many of the previous tests burned at too fast a rate to be of use for field firing of cannon. Finally I reached what I considered a satisfactory burn rate allowing us to fire a cannon twice before it completely burned away.
I wish to share what I have found with others who might have the same interest in discovery that I have.
With this interest in mind I present the formula devised in January 2003 and drawings of two portfires used at the time of the Revolution, one French and one English.
A note on making these: the longer they are left to dry the better the length of burn time will be. I also added two items which need not be used as they are not period correct. One is the match head pressed into the still-wet formula after it has been pressed in the paper tube. This helps light it quickly when in the field.
Second, I used a small amount of railroad flare for the phosphorous to aid the burn rate to slow it down; however, I later found that just using fine sawdust soaked in potassium nitrate and left to dry then repowdered and added did the same thing.
So if anyone out there has the formula used then I would greatly appreciate acquiring it. It was nice to try a portfire several times. It gives one a new respect for the men of that time and their cannon. Note: use a portfire cutter which is easy to make and do not try to put out the cutoff piece using your shoe. Use water.
Portfire Formula
Saltpeter = potassium nitrate = KN03 — 3 parts
Sulfur = S — 4 parts
Black powder = Mealy — 6 parts
Wood sawdust fine, soaked in saltpeter and left to dry — 2 parts
Auto flare ground fine — 4 parts
Linseed oil
The sawdust and flare are added to slow down the rate of burn. Mix the saltpeter the sulfur and the black powder very well first, then add the reground sawdust that has dried in with the powder. Then add the flare and mix well again.
(Note: The flare is optional, just helps it along and is not period correct.)
When all this is done add linseed oil till it is a paste-like substance. Take a 1/2-inch dowel rod and roll a sheet around it. The size is 11 by 4-1/4, the 11 inch the long way. Glue this sheet with just plain white glue and leave to dry. Then glue in a small piece of the rod at the base. About a half an inch will do.
After this is done the tube is ready to be packed wet. Then leave it to completely dry. One of the things I do is to push a broken off match head in at the end to help light it. It’s not period but it works well.
Now for the sawdust I use my sander saw dust and soak it till all the fluid is absorbed and I also while wet add a cap fall of black powder to it also. After it is dry I fine grind it again before adding.
Now to simplify it.
Salt peter 3 parts
Sulfur 4 parts
Black powder 6 parts
Sawdust 2 parts
Flare 4 parts
(optional and not period correct)
then add the linseed oil
Burn rate is about 19 seconds an inch. For a fuse cutter I use a sheep sheers ground with a hole in one blade. This holds the portfire in place as it is cut. A slight twist while cutting pops it right off.
About the Author: Clyde Novak of Lamb’s New York Provincial Artillery and Lauzun’s Legions Artillery of 1781 can be reached at lambsarty@aol.com.