Homemade dextrin

[MadMat]

I recently made some 1/4" cut glitter comp stars. This was my first try at glitter and using homemade dextrin. Now dry, these stars aren't very hard, in fact, I doubt they would survive the burst charge. I made the dextrin by baking corn starch. I read about this online and am wondering if this is just internet B.S. If these stars are junk, at least I only made a small batch (50 grams). I am wondering if it is the binder I used, or I did something else wrong. Anyone else use homemade dextrin with good (or bad) results?

[nater]

Baking corn starch into dextrin is fairly effective, but then resulting product is not as good as the commercial dextrin. The commercial process is more involved than simple baking and converts more of the starch into dextrin.

 

That said, you should be able to make a functional binder at home. I have done it once and the process really stunk. My wife did not appreciate the burning corn starch smell in the kitchen and I will never do it again. Dextrin or SGRS are cheap enough that it isn't worth the trouble to me.

[MadMat]

I understand the chemistry behind commercial production of dextrin involves the use of an acid as well as heat. I thought I would give it a try anyways. Now, is there anyway I can save these stars (maybe heavy priming with a good binder) or are they scrap?

[nater]

Is your dextrin good? Make a 20% solution in water, you will probably have to heat is. If it is sticky, your dextrin is probably good enough.

 

There are a number of reasons for crumbly stars, a poor binder is just one of them. You can always try breaking the stars up and granulating the comp again and cutting or pumping new ones.

[Col]

If its a yellowy/light tan colour it should be good. Put 30ml of water in a glass and dissolve 1g of caustic soda in it, add 30g of your homemade dex and stir until it turns syrupy, Put a thin film of it between your thumb and forefinger and squeeze, if the dex is good it`ll tack up pretty fast and you`ll struggle to get your fingers apart

[schroedinger]

Homemade dextrin works without any problems for me.

Like nater pointed out, there are various reasons for stars to crumble,

Maybe you should explain how you made your dextrin and stars (proces and formula), to get better help.

[MadMat]

I got the formula from this website http://pyrodata.com/composition/filter. I used Winokur #26 comp is:

 

52 Potassium nitrate

21 sulfur

10 Charcoal

6 Bright flake aluminum

6 red iron oxide

6 dextrin

 

I individually screened (except the aluminum) everything through a 40 mesh. Combined everything, ran it through the 40 mesh screen 3 times.

dampened it with 20% denatured alcohol/80% water. mixed it up with gloved hands. Then rolled it into a 1/4" thick flat mass and ran it through a 4 mesh screen to cut them. I set them to dry on a framed window screen. They are crumbly.... Was the denatured alcohol a bad choice?? (I simply can't stand the smell of isopropyl) My dextrin is the right color. I tried simply mixing a bit with a small amount of water and ran it between my fingers; it never felt "sticky" but rather slimy

 

I made the dextrin by baking it in a toaster oven at 375 F. I gave it a stir every 5-8 minutes and cooked it until it was a yellowish tan color. It took a total of about 20 minutes.

 

 

I test fired a small amount of the powder before dampening/forming it and it looked good. Had that thermitey sparkle as I would expect

Edited August 10, 2015 by MadMat

[memo]

my daughter owns a bakery and she makes my dextrin a kilo at a time. it takes about 2 hours to get it a golden brown and it works well. maybe try cooking it a little longer and get a dark golden brown.

 

memo

[Mumbles]

I agree with memo. It's the amount of time you cooked it. It'll take a couple of hours at least, not 20 minutes. I generally did 350F for a few hours stirring every 30min or so, and ramp up to 375 or 400 to get that nice golden color. There are a few ways to check when it's done. Using iodine works to some extent. It turns purple of black in contact with starch (unconverted product), and red in contact with dextrin. I've generally gone by taste however. It tastes starchy or chalky when it's still mostly starch, but begins to taste somewhat sweet when converted.

 

This is all very unscientific by the way.

 

I never experienced this smell that so many people complain about. Maybe I'm not sensitive to it. I always did this in an electric oven, and usually in a glass dish if it makes any difference. There was a faint odor, but nothing objectionable or over powering.

[schroedinger]

Yes your cooking time is to short. I would assume that your brown color was mostly a lighly burning but not dextrin.

[MadMat]

Ah, O.K. Yeah I know about the iodine test for starch. Funny, I never thought to try that out. I more than likely have just toasted corn starch LOL. Thanks guys!

 

So, Do you think I can just redo this comp? I could do the math and increase everything but the charcoal proportionally 5% to make up for the added starch (I assume it will act like a fuel). Or am I being a little to technical and should just go ahead and remake it with good dextrin?

Edited August 11, 2015 by MadMat

[MadMat]

One more question related to these stars I got a formula for burst charge from the same website it went as follows; (I assume it is in parts by weight)

Potassium perchlorate 1

sulfur 1

bright flake aluminum 2

 

I tried this comp out and though it was blindingly bright (exactly what I wanted!) it burned way too slow for a burst charge. I added more KClO4 to a ratio much closer to;

potassium perchlorate 1.5-2

sulfur 1

bright flake aluminum 2

 

This burned much faster! Any opinions on this?

Edited August 11, 2015 by MadMat