Shellac

[Peret]

It's 10pm and I decide I have time, before I go to bed, to make a small (100g) test batch of Lancaster Blue with the shellac that just arrived.

 

Lancaster Blue:

Potassium Chlorate 70

Paris Green 20

Shellac 10

(bind with alcohol only)

 

In about 10 minutes I have it weighed and screen-mixed, and pick up my 100% alcohol spray bottle. (squirt squirt) (mix mix) Still a bit dry (squirt) (mix) STILL a bit dry, doesn't hold together (squirt) (mix). Now it's like damp sand, perfect. I don't waste any time, because I don't want the alcohol to evaporate and leave me with unworkable compound. I load up my star plate and press a batch. They look ok, except they crack after a few seconds. Odd. I load up the star plate and press a second batch. This time they stick to the pins and won't fall off when I press them out. Hmm. I load up the star plate and press a third batch. This time, after momentary resistance, the pins go all the way to the bottom. I pick up the plate and the star comp has flowed through and made a thin sticky patty on the foil underneath. Not good! I think maybe I'll cut these stars after all. I return the mess from the star plate and the first set of stars to the mix and work it all into a patty for cutting.

 

I cut the patty, and to my amazement I watch it flow together and seal up the cuts. I try to work it again but it's turned as sticky as cake mixture and hangs in pointy festoons from my gloves. I leave it on the foil, put it outside to dry, change my gloves and start to clean up. This is a lengthy process that involves painstakingly scrubbing every pin and hole on the star plate with alcohol, and takes well over an hour. The mixing bowl similarly needs scrubbing with alcohol. Paris Green is a paint pigment, and it has "good covering power", as they say in the paint biz. It's a very long time before I can wipe the bowl with a clean paper towel and it doesn't come out green. Finally, at about midnight, I toss the used paper towels in the burn bin and light them up. A large amount of fizzing and blue-white flame comes out of the bin, which surprises me, because this is just clean-up residue, not actual compound. I develop a new respect for the power of potassium chlorate. I take a look at the patty drying on foil. It's become a green amoeba, perfectly smooth and rounded, creeping towards one edge. The top has formed a skin but it's very soft inside and I decide not to risk cutting it again. If it ever goes hard I'll break it up.

 

What I learned from this is that shellac takes rather a long time to dissolve in alcohol, but once it starts there's no stopping it, so one should take one's time when wetting it with alcohol. I reckon it took ten minutes from the first squirt until it became too soft to work, and probably closer to half an hour before it was finished liquidizing. Since the shellac was only 10% of the mixture, and the chlorate and paris green are insoluble in alcohol, it probably only needs something like 1% or less alcohol added, far less than the amount of liquid you add to dextrin bound stars. But when you add that 1%, it still looks dusty dry like nothing happened. I'll try it again and next time I'll wait 15 minutes between squirts.

Edited May 16, 2011 by Peret

[Bonny]

It's 10pm and I decide I have time, before I go to bed, to make a small (100g) test batch of Lancaster Blue with the shellac that just arrived.

 

Lancaster Blue:

Potassium Chlorate 70

Paris Green 20

Shellac 10

(bind with alcohol only)

 

In about 10 minutes I have it weighed and screen-mixed, and pick up my 100% alcohol spray bottle. (squirt squirt) (mix mix) Still a bit dry (squirt) (mix) STILL a bit dry, doesn't hold together (squirt) (mix). Now it's like damp sand, perfect. I don't waste any time, because I don't want the alcohol to evaporate and leave me with unworkable compound. I load up my star plate and press a batch. They look ok, except they crack after a few seconds. Odd. I load up the star plate and press a second batch. This time they stick to the pins and won't fall off when I press them out. Hmm. I load up the star plate and press a third batch. This time, after momentary resistance, the pins go all the way to the bottom. I pick up the plate and the star comp has flowed through and made a thin sticky patty on the foil underneath. Not good! I think maybe I'll cut these stars after all. I return the mess from the star plate and the first set of stars to the mix and work it all into a patty for cutting.

 

I cut the patty, and to my amazement I watch it flow together and seal up the cuts. I try to work it again but it's turned as sticky as cake mixture and hangs in pointy festoons from my gloves. I leave it on the foil, put it outside to dry, change my gloves and start to clean up. This is a lengthy process that involves painstakingly scrubbing every pin and hole on the star plate with alcohol, and takes well over an hour. The mixing bowl similarly needs scrubbing with alcohol. Paris Green is a paint pigment, and it has "good covering power", as they say in the paint biz. It's a very long time before I can wipe the bowl with a clean paper towel and it doesn't come out green. Finally, at about midnight, I toss the used paper towels in the burn bin and light them up. A large amount of fizzing and blue-white flame comes out of the bin, which surprises me, because this is just clean-up residue, not actual compound. I develop a new respect for the power of potassium chlorate. I take a look at the patty drying on foil. It's become a green amoeba, perfectly smooth and rounded, creeping towards one edge. The top has formed a skin but it's very soft inside and I decide not to risk cutting it again. If it ever goes hard I'll break it up.

 

What I learned from this is that shellac takes rather a long time to dissolve in alcohol, but once it starts there's no stopping it, so one should take one's time when wetting it with alcohol. I reckon it took ten minutes from the first squirt until it became too soft to work, and probably closer to half an hour before it was finished liquidizing. Since the shellac was only 10% of the mixture, and the chlorate and paris green are insoluble in alcohol, it probably only needs something like 1% or less alcohol added, far less than the amount of liquid you add to dextrin bound stars. But when you add that 1%, it still looks dusty dry like nothing happened. I'll try it again and next time I'll wait 15 minutes between squirts.

 

 

I had similar problems using shellac a few years ago. The only time I've ever used shellac since, I dissolved the amount needed in alcohol (approx what was needed) before mixing into the comp. It took awhile for the shellac to dissolve (left it overnight IIRC), but I didn't have the same problems. The stars were still sticky, but cut without too much hassle.

[Peret]

I had similar problems using shellac a few years ago. The only time I've ever used shellac since, I dissolved the amount needed in alcohol (approx what was needed) before mixing into the comp.

 

Yes, I thought of that afterwards. The important lesson I take from this is that the amount of solvent needed, be it water, alcohol or acetone, is proportional not to the total weight but only to the weight of those components that will dissolve in it.

 

The toxic and explosive amoeba is still liquid under its skin, 24 hours later. I don't know how to dispose of it, since it will no longer take water. The burn bucket doesn't seem like a very good idea. I may have to take it to a deserted location and ignite it with a long fuse.

[DeepOvertone]

Interesting... I'll keep that in mind. Thanks for the good read!

[Potassiumchlorate]

If the shellac is very fine, it dissolves pretty quickly. I have extremely fine shellac, and I have even rolled stars with it, though it was tougher than with dextrin.

 

For the barium chlorate/shellac star Weingart recommends alcohol only when they are cut. When they are pumped, he recommends dextrin as a binder instead.

 

Another way to make shellac bound stars is to dissolve the shellac in boiling alcohol and add the other chemicals to it. Then you can just pour off the excessive alcohol (you don't even need to filter it) and wait a couple of minutes. Then you have a paste that you can pump to stars. These are very soft before they dry, and the drying time might be several weeks, but it works, and you can use cheaper flake shellac instead of expensive (if bought as such) milled.

 

Off topic: since you have Paris Green, you can try this composition instead:

 

Ammonium perchlorate 70

Paris Green 15

Hexamine 15

 

Or maybe the ratio (I'm not very good at more advanced stochiometry):

 

Ammonium perchlorate 75

Paris Green 15

Hexamine 10

 

NC lacquer as a binder.

 

Myself I only got a small sample of Paris Green, and I might never get hold of it again, but it's interesting to know what you think of this composition. I think this is the blue composition all categories.

Edited October 27, 2011 by Potassiumchlorate

[Potassiumchlorate]

Update: I did some tests with barium chlorate/shellac and isopropanol. It was hard to apply the right amount. First I added 1% isopropanol. Then it evapourated in few minutes. Then I added about 5%. Still didn't stick together. Added about 5% more. This time a part of the composition became too moist and felt like rubber; another part became about as it "should". Pumped 4 10 mm stars. Rolled them in KP/red gum/silicon 70:20:10, since this is a composition hard to ignite, despite the fact that the oxidizer is very powerful. The prime didn't want to stick to the stars very good, despite the fact that red gums dissolves more easily in alcohol than shellac does.

 

They are drying now. Will be interesting to see if this works better than with ethanol, which always contains several % of water, which might be trapped by the shellac.

Edited October 28, 2011 by Potassiumchlorate