No Karo?  No Problem!
Karo Syrup is corn syrup.  Any other brand of corn syrup may be substituted for Karo.  

Dextrose may be substituted for Karo Syrup, yielding a very similar propellant.

Fructose may be added, giving it even better texture.

Golden Syrup may be used by itself to make a good Rcandy.

Also, I have heard that Glucose Syrup works just like corn syrup.  


When I first released the recrystallization process to the Web, I was surprised that some correspondents in other countries asked:  "What is Karo Syrup?"  Well, it is a brand of light corn syrup, so common in the United States that it did not occur to me that corn syrup might be a novelty in other places.  Apparently it is. 

Correspondents from several other countries could not find it.  A friend who went to vacation in Australia was sent to spy on the supermarkets, where she was unable to locate any brand of corn syrup.

Someone on SugPro (apologies, I forgot who) sent me the list of contents for Karo Syrup, indicating it is primarily water, dextrose, fructose, and lesser amounts of other sugars.  

Hoping that dextrose alone would offer the texturizing benefits of corn syrup, I tried this formula:

100g KNO3
  30g sucrose
  20g dextrose
     5 tablespoons (50ml) water 

It is processed the same way as in the original recipe, brought to a boil, poured into glass pie pans, and cooked until dry.  The dry flakes are scraped up while hot, pressed into a cake, and kneaded until they consolidate and form a cohesive texture like clay or putty.  This SU/DX version is a little harder to consolidate than the traditional recipe, and required double-mixing.  By that I mean that when the propellant is dry enough to pass the "snap test" it should be scraped up and patted down as much as possible, returned to a 250 degree oven for 15 minutes or so, then worked again like a dough to develop its cohesive texture.

When feeling lazy, I put the hot flakes in my food-processor, which assists in development of good texture.  Sometimes it was necessary to remove the propellant from the food-processor, return it to the oven to re-heat, and process again.

The proportions given here are subject to refinement.  Thanks to Richard Nakka for pointing out to me that my "dextrose" is actually dextrose monohydrate, with each dextrose molecule attaching to one water molecule accounting for 9 percent of its weight.  Thus this propellant is a bit oxidizer-rich, at 67.5 percent KNO3, 32.5% sugars. 

The difference is due in part to the elimination of Karo Syrup, which contains some sugars, and also my failure to account for the dextrose containing 9% water.  I had noticed that a burning strand forms little "pearls" of white fluid, which I had seen with variants having a high proportion of oxidizer.  In a static test, this propellant burned through the side of an aluminum motor case , making me realize that oxidizer-rich candy tends to burn hot, just as Mr. Nakka has indicated.  My traditional method with Karo Syrup is on the fuel-rich side, thus cooler-burning.

As a side-benefit, su/dx rcandy seems to be a bit less hygroscopic than that made with Karo Syrup.  This is perhaps because Karo contains fructose, as pointed-out by Mr Bill Westfield, which is more hygroscopic than sucrose or dextrose.

Tri-Sugar:  Sucrose, Dextrose and Fructose
Even better!  

In an effort to simulate corn syrup, I have been reverting to the original formula, but adding some dextrose and a little fructose to the mix.  I find this produces a much nicer texture than sucrose/dextrose alone, and is comparable to the original rcandy made with corn syrup.  The proportions are 64% KNO3, 28% sucrose, 6% dextrose, and 2% fructose.  

Here is the recipe:

100g KNO3
  44g sucrose
  10g dextrose
    3g fructose
    5 tablespoons (50ml) water 

This should yield a propellant with about 36% total sugar and 64% oxidizer, discounting any residual moisture.  Thus it would be slightly fuel-rich and thus cooler burning.

Golden Syrup Rcandy:  

Several correspondents have asked me if "golden syrup" might be used in place of corn syrup in the rcandy recipe.  It is specified as a replacement for corn syrup in many recipes, so would it work here?  I tried it, and it didn't work well at all.  Golden Syrup is "invert syrup."  That is, it is sucrose which has been partially broken down into its respective monosaccharides, fructose and glucose.  But apparently it was not inverted enough to be a direct substitute in the standard recipe, making a crumbly propellant

But today, whien entertaining this question from a new correspondent, I began to wonder if the proportions of sucrose, fructose and dextrose might be close enough to make good propellant.  Tried it, and it works!

100g KNO3
60g Lyle's Golden Syrup
100g hot water

Hot water, to dissolve the Golden Syrup and get it out of the weighing container.  Afterwards, it was processed with the electric skillet method, requiring about 30 minutes to get a good working texture.  It seemed a bit powdery at first, but with repeated stirring as it cooled, a very good texture was achieved.

Used in a 38-240 motor static test, this propellant burned at roughly half the speed of conventional rcandy.  This with just one test, so needs further testing to determine why.  

Hopefully this will be useful to some.  I will continue to experiment with su/dx and report any significant findings.

Back to rcandy page

Jimmy Yawn 

rev. 12/2/06