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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.
Some notes concerning these formulae:
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.
In 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.
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 Compositions
For 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 composition
0.44 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.
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.
A 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 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.
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Well, 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.
Read and review these Fireworks Safety Articles before starting any fireworks project.