Dextrin

Dextrin is used to hold things together. It binds our pyro mixtures so they don't fly apart or crumble easily. While there are differing opinions about which binder to use, dextrin is probably the most commonly used pyro binder in the U.S. 

Dextrin is a fuel but it is used in very small quantities and does not contribute much to our pyrotechnic reactions. In larger quantities, it can retard the speed of burning in BP and star mixtures. It is water soluble and is easy to purchase and easier to make.

Here is a table about the different dextrin types - we want to concentrate on yellow dextrin. White dextrin and British Gum are not as suitable for our uses.

The following table is from: http://www.specialchem4adhesives.com/resources/articles/article.aspx?id=757#t and shows the results of baking cornstarch to create dextrin.

Property
White Dextrin
Yellow Dextrin
British Gum
Roasting Temp., C
120-130
135-160
150-180
Roasting Time, hrs
3-7
8-14
10-24
Catalyst Concentration
High
Moderate
Small
Solubility
1-95% in water*
Very soluble in water
1-95% in water*
Viscosity Stability
Prone to retrogradation
Good stability
Good stability, higher viscosity than Yellow
Color
White - Buff
Yellow - Tan
Yellow - Brown

In the above table, we see that Yellow Dextrin requires 8-14 hours of baking at 135-160 degrees Celsius (320 degrees Fahrenheit). Most hobbyists speed up the conversion by upping the heat to about 200 degrees C. or 400 degrees F. The catalysts mentioned in the table above are acids and are almost never used in hobbyist dextrin making.

Making Dextrin

Borrow the family oven, get a large pan, a pound of cornstarch, and a metal spatula.

Bake at 400 F, stirring every 15 minutes, until golden tan/brown

Screen before using.

 

Heat the oven to 400 degrees, spread the cornstarch out in the large pan and bake it for 15 to 20 minutes. Stir, and bake again for 15-20 minutes. Repeat until you have golden tan/golden brown dextrin. Screen it and use it according to the formulas. Don't worry if it isn't pure - just go for the color and it will work fine.