Some interesting Visco Facts

[Doc Wally]

A few facts you may find interesting about 3/32” / 1/8” Visco 5 /12 fuse with 2 coats of Nitrocellulose lacquer. Visco was developed for the fireworks industry as a reliable, inexpensive ignition source for 1.4 type fireworks. Prior to Visco, manufactures user several different types of paper wrapped black powder fuse such as what was used in early 1½” firecrackers. This type of fuse worked well for what it was intended but as we all know it was delicate and easily damaged. Larger devices like the 2” X ⅜” crackers, (Big Bang) brand for example used the same type paper fuse but of a higher quality and a slightly larger diameter. In order to insure the article worked, the manufacture would use a double looped fuse of this paper type to more insure ignition. With this looped “double fuse” the odds were it went off much more reliably than a single fuse. With the advent of Visco, ignition was much more reliable and a greater safety factor was achieved. To the point. Visco was never intended to be used as a timing type fuse. It does have a precise burning rate and was only designed to be a non-timed source of ignition. Yes, it is used for igniting many types of 1.4 fireworks, but is only a slow burning source of ignition (as compared to quick match and other types of fuse). It is also what referred to as a self-consuming type of fuse. This is imparted by the Nitrocellulose that it is encapsulated in. The first coating of NC is thinner than the second coat. The reason for this is so the NC can soak into both layers of cotton fiber and seal it to prevent core loss during manufacture. The second coating is again NC but much more viscous with several additives to impart the quality’s required. If Visco of the proper burning rate is used where it is totally surrounded by a fireproof media with both ends left exposed, it can and has been used for small aerial type consumer products with fairly uniform ignition timing results, but since the flame front does penetrate the NC jacket the exact burst timing of a small shells cannot always be guaranteed to be the same like our very consistent 1.3 products. The only time that it could be relatively consistent would be the portion of fuse that is totally encapsulated. Anything above or below that portion could ignite or be ignited at any time once initiated.
Doc Wally

[Rick_In_Tampa]

Very interesting Doc. So let me ask you this. We all know there are different burn rates for the various fuse types out there. Is that burn rate achieved based more on the type and amount of NC product and the paper type used for the fuse? Or is the black powder charge inside made differently to burn at a different rate? Or maybe a combination of all three??

[Doc Wally]

Thanks for the Question Rick_in_Tampa. The burn rate of most fuse is dependent on all three criterion you have mentioned. The nitrocellulose and paper to a lesser degree of the three. We use a combination of many different types of flammable powders to achieve the burn rate we are looking for or a customer requests. For standard consumer visco sold over the counter with a burn rate of about 35 seconds per foot we use a combination of 7F-Meal D- willow charcoal and potassium nitrate and sulfur. To speed up the burn, you would use more 7F in relation to your other ingredients and to slow it down you would use more charcoal and saltpeter.
Doc Wally

[Rick_In_Tampa]

I knew I should have paid closer attention in chemistry class! lol... This whole area (fireworks in general) is fascinating stuff. Most people just like to lite a fuse and go "Ahhh" and "ohhh" after the boom. There is just sooooo much more involved than people realize. Thanks again Doc for the explanation!

Now let me ask you a really stupid question! Do you still put on your own fireworks shows? Or has the shine faded away after all those years in the business?

[Doc Wally]

Rick_in_Tampa, Good to hear from you! Any time Rick, I love to answer questions if I can. By trade I am a chemical engineer. But enough said about that, and yes chemistry is a boring subject to most but a necessary part of life especially when your into things such as pyrotechnics like so many of us. It’s good to know some basics in chemistry to understand why things work the way they do but you learn most of what you need to know from our comrades. To answer your question. I started shooting 1.4 “back then class C common fireworks” when I was about 10 years old. Luckily my dad was a fireworks lover also I guess you could say he got me interested in the art. I made it a point to learn as much as I could about fireworks whenever I could. Now jumping ahead a few years. I was lucky enough to meet up with some extremely nice professionals doing shows at a local amusement park. These are the people that were already in their 50s and 60s, mostly all gone now. They were all of Italian decent and that is the art form that was taught to me. Well, I remember my first show! Joey “my mentor” let me light and that was it. Believeeee meeee. It is the smoke and don’t let anyone tell you it isn’t. The years passed and I spent every minute at the factory I could spare. I still had to make a living but the month or 5 weeks before the 4th of July, I took my vacation and many nights I actually slept under the fireworks bench at the shop on an old Army cot. Things were very different back then! I have been doing shows since and I am still doing them now. I just finished up 6 shows with the crew for the 4th. and have a few more celebrations coming up. Your question is by no means stupid! I get asked that very same questions many times. No, the shine hasn’t tarnished one bit and never will. The sad part is I really can’t do much heavy work anymore but we have a great crew of young blood that handles that. A lot of people come and go but that’s ok, a few special people “Smell the Smoke”.

[Rick_In_Tampa]

That's a great story! Sounds like you definitely had a calling for this line of work from a very young age. It's great if you can grow up and do something you love for a very long time, and make a good living at it in the process. I've always loved fireworks too, but I smelled a different kind of smoke made by JP4. lol... So I spent 22 years in the Air Force after I graduated from HS. Not a lot of pyro going on during that time for me. But I'm certainly making up for lost time now! I'd love to get on a professional crew and help set up some shows. I'm too much of a medical misfit to do what the young kids can do, but I can still learn and be taught so... I'm holding out hope. Until then, I'll keep doing what I'm doing with the 1.4 products. It's a lot of fun, and the family and neighbors really seem to enjoy the shows. What more can I ask for!?

[Pyro Paul]

Hi Doc, some great stories so far. I'm glad that Dave brought you into the group. I got to wondering while I was reading your last post, I'd like to hear about lessons learned in your life in respect to pyrotechnics. I have a family member that has a degree in chemistry and I talk with him for hours when I get the chance. I wish I'd have written all the stuff he's told me about so that I could always have the information. He is the single greatest inspiration in my life when it comes to pyrotechnics and introduced me to class B fireworks many years ago. Sometimes some of the chemistry talk goes over my head but he explains things thoroughly enough that I get the gist of what he's saying. Thank God I did pay some attention in chemistry class. lol So anyway just wondering if you could drop some pearls of wisdom on our young ears of lessons you've learned while "smelling the smoke".

[Doc Wally]

Great story Rick! Wow, 22 years in the Air Force. That’s a long time to live on JP4. Thanks for your service. Yes I can’t explain it but I really love fireworks and I have made a good living at it. Now I want to continue it as a retirement hobby for as long as I can. As you well know, they have some really great 1.4 products today that when choreographed well can produce a spectacular show. I have to say that several times I have squeezed in several 1.4 items where they can be seen really well like on flat ground with no obstructions between them and the spectators. You would be surprised, then shoot a few B-cakes behind them and then a few 3 or 4 inch shells over the top, it looks really great. Take your time, have fun make people happy and then go for your license (if you want). I’ll tell ya, at the end there is nothing like the roar of the crowd, it’s the icing on the cake!

[Doc Wally]

Hi Paul, Great to hear from you! That’s wonderful having a family chemist you can refer to. Tell ya what he is worth his weight in gold when it comes to pyrotechnics and many other things too. It’s interesting my sister is a Bio Chemist, I majored in organics (Resin Chemistry) and my daughter is in aerospace engineering. Boy when we get together we have a blast talking tec. But other than that, yes I have lots of stories from over the years that I have experienced. Being educated in the sciences is great but as you can imagen it isn’t everything. It gives you a good background on what is going on in the world around you but you need the experience and the input from those who know and have been around the block a few times. These are the type of people I learned from. I have to honestly say I know a bit about fireworks but there are people out there right now and the people I learned from who have passed on who make me look like a neophyte! I learned from some of the best people of their time but now there are great young people out there that will carry on the art. Tell you what I would love to do, as you can see I’m a bit long winded but that’s the way us Chem Geeks are! I will post a story every so often on a subject that I have personally experienced and learned from, good or not so good that I think you would like to read about. Give me a few days and I’ll crank one out.
Doc Wally