How to Make Colored Gerbs
IntroductionIn Making Gerbs (Fountains) I introduced a method for making homemade fountains, called gerbs, including how to make the tools for ramming them. I later explored a few creative devices using fountains.
Homemade Silver-Titanium Fountain
I was ready to move on from gerbs, but then I received a note from Paul N, a loyal Skylighter customer. In his letter, he began by referring to his homemade waterfall, in which he used consumer fountains.
In part, Paul said:
"I used a tube fountain from a local C shop and using rebar tie wire to hang them between two trees in my front yard, and the superfast paper firecracker fuse I got with the Skylighter mortar tubes special, the thing TOOK OFF and was brilliant. 20 feet of BRILLIANT! As they burned out, a secondary fuse lit some suspended large "colored flowers" firecrackers which just ROARED. It was a serious crowd pleaser. Even now I am still jazzed, and you can tell Mr. Gilliam I said so. Now that I have that concept down, I want to make a curtain of color, and I need to get or make RED and BLUE fountains (er, gerbs.) I have, as they say, an idea. Can you tell me of formulae for making red and blue gerb comp?"I of course did not relay this message to Harry, lest he get an even bigger head about the service he provides to us pyro fanatics. I could sure relate to Paul's enthusiasm and inspiration. How often I have felt that same way.
I have never seen colored consumer fountains at local shops that might be used in the way that Paul envisions.
I like to use colored fountains as one of the stages in devices like wheels and girandolas (horizontal flying wheels). Just recently I was giving some more thought to homemade colored gerbs, and had dug out a past PGI Bulletin article by John Glasswick, entitled Gerb Colours.
John is a friend of mine and a master pyro craftsman, his gerbs and wheels are something to see. We see one another just once a year at the PGI conventions, and we have often competed against each other with our wheels or ground displays. It has been no disgrace to have him beat me in a competition, and it's been a real honor the few times I've edged him out in points.
John Helping Ned Prepare a 24-Inch Girandola for Flight at the 2007 PGI Convention in Fargo, North Dakota
John hails from Canada, and spells words funny, like colour and splendour, but we won't hold that against him. He graciously allowed me to use the information in his article as the foundation for this one. In that essay, John relates that he got many favorable (favourable) comments about the colors of his gerbs one year at the convention, along with quite a few requests for his formulae.
John started with a favorite red formula that had been shared by Tom DeWille on the Pyrotechnic Mailing List several years back. This red formula was slightly modified to create the other colors, with one exception; blue.
The blue composition came from Joel Baechle's Pyrocolor Harmony, to which John added 15 parts titanium for sparks. About that book, John states, "I found Joel's book well worth purchasing, and the book has also been invaluable for me for star colour formulas."
Note: There is another nifty blue gerb formula and method described by Mr. Gilliam in this article, Blue Steel Gerbe.
So, rather than quickly moving on from the subject of gerbs, why don't we spend one more week on them, and explore color gerbs.
Colored Gerb Composition FormulaeThe following are the formulae from John's article, as well as Joel Baechle's blue composition, to these formulae John added 13% titanium. I use either fine spherical titanium such as CH3010, which produces a short, dense spray of fine sparks, or the coarse spherical Ti such as CH3001, which produces a long spray of larger silver sparks.
If you want a simple colored flame with no silver sparks, the titanium may be omitted completely. It could also be replaced with ferro-titanium if less brilliant, yellow-silver sparks are desired, or even coarse charcoal for a softer, orange spark spray.
|Blue Gerb Composition
|Ammonium perchlorate, 200 micron
|Black copper oxide, or red
|Aluminum, 325 mesh fine flake
|Red Gerb Composition
|Magnalium, 200 mesh
Green Gerb Composition
Same as above except substitute barium nitrate for the strontium nitrate.
Note: I ended up using only these three basic color compositions. Other colors were made by combining these comps in various ratios as described later on.
I will include John's other formulae, though, as listed below:
Lime Gerb Composition
Same as green except use 0.43 barium nitrate, and 0.01 sodium nitrate.
|Yellow Gerb Composition
|Magnalium, 200 mesh
|Orange Gerb Composition
|Magnalium, 200 mesh
|Purple Gerb Composition
|Magnalium, 200 mesh
|Black copper oxide, or red
|Turquoise Gerb Composition
|Black copper oxide, or red
|Magnalium, 200 mesh
Some notes concerning these formulae:
- Strontium nitrate and sodium nitrate are hygroscopic, which means they will readily absorb moisture from the air. They should be stored in tightly sealed containers, and dessicant packs stored with them will help keep the chemicals dry. It can be helpful to dry the chemicals prior to using them, by spreading some of the chemical out on a kraft-paper-lined cooking sheet and heating it in a 200-degree oven for 2 hours.
Warning: I repeat, this oven-drying is only done with these individual chemicals, never mixtures.
Once gerbs are made using either of these chemicals, they should be burned in short order or they should be stored in tightly sealed containers (ziplock baggies work well) with some dessicant packs.
- Barium compounds are toxic, and simple precautions such as wearing gloves and a respirator will prevent them from being absorbed through the skin or lungs. Some folks are very sensitive to barium, and I've heard tales of those who have suffered its poisoning. It does not sound like fun.
- Some folks substitute saran for parlon with good results.
Yellow - 0.25 red, 0.75 green
Orange - 0.60 red, 0.40 green
Chartreuse - 0.14 red, 0.86 green
White - 0.14 red, 0.28 blue, 0.58 green
Purple - 0.60 red, 0.40 blue
Aqua - 0.25 blue, 0.75 green
Similarly, the Veline color star formulation system, found in Tom Peregrin's Introductory Practical Pyrotechnics, starts with four basic color compositions, red, green, blue and orange, and mixes them to obtain other colors:
Yellow - 0.45 orange, 0.55 green
Chartreuse - 0.20 orange, 0.80 green
Aqua - 0.20 blue, 0.80 green
Maroon - 0.85 red, 0.15 blue
Salmon - 0.25 red, 0.60 orange, 0.15 blue
Purple - 0.15 red, 0.05 orange, 0.80 blue
I've always found it interesting that these basic color comps are not combined in the same combinations that paints would be. They are rather mixed so that the light they emit combines to give the appearance of a completely different color. I used these color-combining methods to achieve the other various colors of gerbs using the basic color compositions: red, green, and blue.
Priming/Starting CompositionsIn his article, John states, "I have found the compositions difficult to ignite, but I have had no problems as long as they are primed with a 50:50 mix of black powder/gerb composition."
In the Making Gerbs article I described a Starting Fuel composition. I rammed one increment of this fuel before introducing any standard fuel, especially in gerbs where I was going to be drilling the nozzle aperture with a twist-drill. This prevents sparks during that drilling.
This Starting Fuel is perfect for priming the gerbs as John describes. The first rammed increment above the nozzle will be Starting Fuel. The second increment will be 50:50 Starting-Fuel/gerb-composition. Then increments of the colored gerb composition will be rammed.
This is called "step priming", and is a common practice, especially when rolling round stars, when a low-temperature composition is going to ignite a high-temperature one.
This will work well to ignite our color gerbs, with one big exception. No composition containing ammonium perchlorate may be in contact for any length of time with a composition containing potassium nitrate, such as the Starting Fuel or any other standard black powder composition.
This is because the combination of potassium nitrate and ammonium perchlorate forms extremely hygroscopic ammonium nitrate within a short amount of time. If you try that combination, you'll soon end up with a soggy mess which will not burn.
You might try standard priming if you're going to ram your blue fountain and take it right out and burn it.
But, with the blue gerb comp which contains ammonium perchlorate, or any color mixture which contains that composition, we have to have a different first-fire/priming mixture if the gerbs will be stored for any length of time.
|Potassium Perchlorate First Fire Composition
This composition will be used to ignite the ammonium perchlorate containing gerbs in the same step-priming fashion described above.
For simplicity, it actually can be used to prime any of these color gerbs.
Mixing Gerb CompositionsFor this project, I want to make several of each type of gerb in the basic colors, and I want to try mixing the basic compositions to form the other colors. So, I want to mix up 16 ounces of each of the red, blue, and green formulae for starters.
I think I'll make up those basic mixes without the titanium in them. I can then see what they look like with just the colors, and then I can add the Ti to the mix for individual gerbs to see how they look with that metal in them.
Many of you may know this, but there is a nifty way to remember the basic colors of the rainbow: Roy G. Biv: Famous pioneer in paint coloration. Well, maybe not.
Red, Orange, Yellow, Green, Blue, Indigo, Violet (Indigo is the bluish purple, and Violet is the reddish purple, and I usually just lump them together as purple when I think of the rainbow.) ROYGBIV
So, I want to make a rainbow of colored gerbs.
To make a 16 ounce batch of one of the formulae, I take the decimal ratio of each individual chemical, and multiply that decimal by the final batch size to arrive at the amount of that chemical to use. For example:
16 ounces of red gerb composition0.44 x 16 = 7.04 ounces of strontium nitrate
0.17 x 16 = 2.72 ounces of parlon
0.17 x 16 = 2.72 ounces of magnalium
0.13 x 16 = 2.08 ounces of titanium
0.09 x 16 = 1.44 ounces of red gum
Total = 16 ounces
(My little digital scale weighs to the nearest 0.05 ounce, so I round the above amounts to the nearest 0.05 ounce, to get 7.05, 2.7, 2.7, 2.1, and 1.45 ounces, respectively.)
I then add all the individual chemical amounts together to make sure that the total is about 16 ounces (may vary a bit due to number rounding). In this case the total comes to exactly 16 ounces.
After weighing the chemicals out individually, I screen them one at a time through a fine-mesh kitchen colander, into a bucket. I check the weight of the complete composition and make sure it is very close to the original total batch weight I wanted. This ensures that I didn't miss a chemical, and that I weighed each one accurately.
Note: If, during the screening, I discover that any of the individual chemicals won't pass the screen, I mill that single component in a small coffee grinder until it is very fine. I have a mill that is dedicated to fuels, and one that is used only on oxidizers. I never put metals into any of the grinders.
Screen Colander, Bucket, and Coffee Grinder for Milling and Mixing Gerb Fuels
I put the lid on the bucket and shake it a bit, to thoroughly mix the contents. Then I gently screen the mix one more time through the colander to break up any remaining clumps of chemical.
I did not granulate these compositions. I did use rubber o-rings on my tooling drifts to keep the loose comp from fluffing out when the tooling was inserted into the tubes.
Ramming GerbsA few more tips from John Glasswick's article will come in handy now.
He does not press his gerbs, but simply compacts the compositions with his body weight on the tooling. Since the nozzle clay really holds up best when it is solidly compacted, I decided to ram the nozzle as I usually do, with 12-16 rawhide mallet blows. I used bulkhead mix without any grog in it since I plan on hand-drilling the hole in the nozzles.
After the nozzle was rammed, I started with a flat half-tablespoonful of the starting fuel, and consolidated that increment with 8 light hits with the mallet. I followed the starter fuel with an increment that consisted of 1/2-teaspoonful of starter fuel mixed with 1/2-teaspoonful of gerb composition. I simply mixed these fuels in a paper cup with a gentle swirling motion before introducing the mix into the gerb tube.
Note: Since I'm ramming the blue composition which contains ammonium perchlorate, and I'm planning on mixing that comp with other colors to produce color-mixes, I actually just used the potassium perchlorate first-fire composition for the priming of all the gerbs I made for this project.
Then I rammed increments of gerb fuel and finished off with a clay bulkhead, just like any standard gerb. I rammed all of these increments with the same 8 gentle drops of the rawhide mallet.
Note: One of the reasons John does not pound on his compositions is that they contain sponge titanium which he uses. Rough metals like that can cause sparks when they are hand rammed with a mallet. I'm using smooth spherical titanium, and I consider this to be safer to hand ram, although I am using gentle hits when I do this with these formulae. It is best to do this outdoors with no large quantities of exposed compositions just in case any accident occurs.
John notes that he uses thicker walled tubes for these gerbs because they burn hot and can burn through the walls of thinner tubes. I used 1/4-inch wall tubes throughout these gerb projects.
And, finally, because these compositions have magnalium in them, among other ingredients, they produce dross or slag when they burn. This dross can tend to clog a narrow nozzle aperture, so the holes that we'll drill in these nozzles will be on the large side. For these 3/4-inch ID tubes I'm going to drill 3/8-inch nozzle holes. 5/16-inch ones might work, too, and would produce a bit more thrust and a higher spray of sparks.
I rammed a gerb in a 7.5-inch tube using the blue composition, without any titanium in it. It ate up 1.9 ounces of the blue composition, and once the starting fuel increments burned, it produced a really nice blue flame about 10-inches long. The fountain burned for one minute.
The same gerb, using 1.75 ounces of blue comp and 0.25 ounces of titanium, mixed in a paper cup prior to ramming, burned exactly the same except it also produced a nice 6-foot tall spray of bright silver sparks.
Blue Gerb Without Titanium
Note: I am not cropping these gerb photos so that you can see their relative brilliance by comparing how much of the surroundings light with each one.
I rammed a red gerb in a 7.5-inch tube, without any titanium in it. It took 2 ounces of the composition to do this. After the first-fire increments burned, a brilliant 8-inch red flame spouted forth for 60 seconds. But, the tube sidewall did burn through for the last 10 seconds and a lot of the flame started spewing sideways out of that enlarging hole.
The gold-glitter and silver-titanium gerbs I made a couple of weeks ago only burned for about 30 seconds, so I could settle for a 30 second burn with these color gerbs as well. To accomplish that, looking at the sketch of a gerb and noting that the actual fuel grain in the 7.5-inch tubes is a little over 5 inches long, I could start with half that fuel grain. This would result from ramming the gerbs the same way, but starting with a 5-inch tube.
A red gerb in a 5-inch long tube, rammed with 1 ounce of composition, burned for exactly 30 seconds, with no tube sidewall burn-through. It's hard to overstate the brilliance of these red gerbs. Man, they are fierce!
My assistant in these comparisons was my granddaughter, Michelle, and the red gerb was her favorite by far.
I added 0.15 ounce of titanium to 1 ounce of the red comp and rammed that in a 5-inch tube. That gerb burned identically to the one above, but with a 6-foot spray of silver sparks. Very nice.
Red Gerb Without Titanium
Since the green gerb composition simply replaces the red's strontium nitrate with barium nitrate, I expect it to perform similarly to the red. (Famous last words.)
So I'm going to try 1 ounce of the green comp in a 5-inch tube. (It actually only took 0.75 ounce of the comp.) This gerb burned with a brilliant green for exactly 30 seconds, with no tube burn-through.
0.10 ounce of titanium added to the 0.75 ounces of green fuel produced the same effect, with the addition of the silver sparks.
Green Gerb Without Titanium
For starters, I thought I'd try something simple to produce a yellow gerb: a combination of the red and green comps I already had mixed up, in a 0.25/0.75 ratio, as the Kosankes recommend with their lance method.
So I took 0.25 ounce of the red comp and 0.75 ounce of the green and mixed them together. That mixture got rammed into a 5-inch tube, and I had 0.10 ounce of the mixture left afterwards.
That gerb burned with a brilliant yellow flame, similar in brilliance to the red and green gerbs. I did notice a bit of a green tint around the edges of the flame, so I tried one with 0.30 red and 0.70 green to see if I could balance it on the yellow a bit better.
I did like the more pure yellow color of that mixture better.
Yellow worked, why not try the Kosanke proportion for orange: 0.60 red/0.40 green.
A 5-inch tube, burned with a brilliant orange flame for 30 seconds. The color looks more like red in the photo and video, but the gerb definitely had a brilliant orange color to it.
One more color to try out. I prefer a purple that leans toward the blue end of the spectrum: an indigo. So rather than try the Kosanke 60/40 red/blue, I thought I'd try something more along the Veline proportion: 0.20 red/0.80 blue.
Oh, man, really nice 30 second purple fountain tending toward the blue end of the spectrum, just like I like it.
I decided to try out my standard gerb tooling which automatically forms a 5/16-inch hole in the nozzle, rather than hand-drilling a 3/8-inch hole in a solid nozzle. This should increase the pressure inside the tube during the burn, and also increase the possibility that the dross formed by the burning fuel will clog the nozzle as it burns.
I used a 5-inch tube, 0.75 ounce of the red fuel to which I added 0.10 ounce of 36 mesh charcoal. This gerb burned for 30 seconds with a flame that was similar to the gerbs with 3/8-inch nozzle holes. It did produce a nice, soft, 5-foot tall spray of orange sparks which did not detract from the brilliance of the red flame.
Note: One more time, remember to begin each gerb with an increment of the starter fuel, and then one of 50/50 starter fuel/gerb composition.
A Complete Rainbow of Gerbs with 36-Mesh Charcoal Sparks
ConclusionsWell, I have ways to make each of the 6 colors of the rainbow in brilliantly burning 30-second gerbs: Red, Orange, Yellow, Green, Blue, and Purple.
These colors, and other possible combinations, all start with only 3 basic color compositions: Red, Blue, and Green. I really have to try Aqua, one of my favorite colors, and then there's chartreuse. What color is chartreuse, anyway?
And, if I want to I can make a blue fountain that burns for 60 seconds. (I suspect it is the magnalium in the other mixes which burns so hot that tube burn-through begins at 45-50 seconds with them.)
I can add the titanium to the compositions for a tall spray of silver sparks, or the gerbs can be burned with only the brilliant colors illuminating everything around them.
These fountains will make great additions to wheels and girandolas, and in the back of my mind I can imagine them lined up on a frame, shooting their flames on an angle, and creating designs and letters with them.
So many projects, so little time.
Paul, I hope the red and blue gerb compositions fit the bill for the "idea" you have in mind for your next backyard-waterfall project. Michelle's favorite color is the red, and mine is the blue with the gentle orange charcoal sparks.
Thanks to Tom DeWille, Joel Baechle, and John Glasswick for blazing a path which we can follow when creating these beautifully colored flames.
Stay Green, and red, orange, yellow, blue, and purple, too.