Rcandy Not working properly

[kevinH]

i have tried PN 60g & sug 40g but when i was cooking with 20 drop of water it gets very dark in color just after when both melts and after that when it was still in much liquid state or i will say when it start to get in a bit thick it suddenly gows off on the pan

y?

what i have to do to make it light in color

& what i have to do to not make gows of in the pan when i was still cooking?

what i have to do to make it less sensitive cos i have to ship it 300km on my solder bag

[pyrokid]

It sounds like you are cooking it too hot.

 

I don't think sugar fuel is too sensitive when it isn't hot. Hygroscopicity would be a bigger concern for me.

[schroedinger]

You are cooking if way to hot. Use an oil bath for cooking your rcandy

[Oinikis]

As the guys say, cook colder. My method, 2 parts KNO3, 1 part Sugar, 0.5 parts water (33.3 % is near perfect). Put water and nitrate in a wide can and heat until it's like 40-50 centigrade, so most or all of the nitrate is dissolved, then drop sugar, and mix it nicely. Heat it until it starts burbling and keep the heat as small as possible, while water is still evaporating. Mix nicely, basically non-stop, and make sure you get the bottom, becouse that's where overcooking happens. When it get stiffer, take small samples, and put them aside, and let them cool. If it's still soft or bendy while cold, throw it back and cook more. Cook until sample is rock hard, when room temperature, and breaks when force is applied. Then you can do burn test if you want (Do not leave rcandy alone for more than a minute, and do the test at safe distance from the batch). It should burns several mm/s. Anyway, when you reach the point when it's rock hard when cold, that means it's done and you can cast it. It takes some practice, but once you get it, then you'll get consistent results.

EDIT: Use an electric stove, you don't want to make rocket fuel on a gas flame.

Edited September 16, 2014 by Oinikis

[dagabu]

Bottom line: Gas flame just doesn't work, James used an oven then went to an electric skillet, they are cheap at the Goodwill (or similar) store and are controllable. Do the rest as Oinikis says...

[Jakenbake]

Are the benefits of casting the comp that great? I always used to grind my kno3 in a coffee mill. Then mix with powdered sugar. And start pounding out rockets. What am i missing?

[schroedinger]

Well casting is much less work and gives far better results then just ground stuff, have a try and compare both then you will see the difference.

[Oinikis]

Melting mixes chems on molecular level, makes grains stronger, and more consistent in terms of burnrate and density.

[kevinH]

thank you all

[modelrocket]

Bottom line: Gas flame just doesn't work, James used an oven then went to an electric skillet, they are cheap at the Goodwill (or similar) store and are controllable. Do the rest as Oinikis says...

I've been using a gas flame for all my smoke bombs and haven't had a single batch that was too dark or ignited. Obviously electric/oilbaths etc is better, but if you don't have acces to that kind of machinery (XD) you have to make due with what you have... just keep the flame small and stir alot..

 

You are obviously over heating the sugar, but not only that, you should use more water too.

 

Given that the sollubility of KNO3 in boiling water is 250 grams/100ml and that of sugar about 450 grams/100ml

20 drops of water equals 1 milliliter of water...

for the KNO3 you need 24 ml and for the sugar 9ml, and because water evaporates rather easily I'd use a safety factor of 100% (for these small amounts). So imo next time use 65ish ml of water.

 

 

Also just saying, KNO3 doesn't melt and neither does sugar. 2KNO3 decomposes into 2KNO2 + O2 at about 400 degrees Celsius and tablesugar decomposes into glucose and sucrose at about 180 degrees Celsius.

[modelrocket]

Are the benefits of casting the comp that great? I always used to grind my kno3 in a coffee mill. Then mix with powdered sugar. And start pounding out rockets. What am i missing?

 

 

Melting mixes chems on molecular level, makes grains stronger, and more consistent in terms of burnrate and density.

^^ BS. (edit: only the "mixes chems on molecular level", the rest is true)

 

When you use the melting technique you don't melt the KNO3, only the sugar decomposes into glucose and fructose which are liquidy at that temperature. When you mix this with the KNO3 and let it cool the glucose and fructose will fill all the space between the KNO3 particles, this is way better mixed than just ground and pounded.

 

HOWEVER, the recrystalizing method is superior in mixing, this is because BOTH the KNO3 and sugar will sollute?(idk the word), when you cook the water out the sugar and KNO3 start to recrystalize, giving you a near perfect mix where the chems are mixed on a molecular level.

Edited October 23, 2014 by modelrocket

[dagabu]

BUT...If you are cooking indoors in the kitchen then it is pure foolishness no matter what the heat source.

[modelrocket]

BUT...If you are cooking indoors in the kitchen then it is pure foolishness no matter what the heat source.

Definately, always outdoors. (except ofcourse if you have a laboratory...)

[modelrocket]

It sounds like you are cooking it too hot.

 

I don't think sugar fuel is too sensitive when it isn't hot. Hygroscopicity would be a bigger concern for me.

I'm going to do a stress test to alot of different r-candies soon (different methods/formulas etc).

 

It will be a basic test though, I'm going to shoot sparks at it with an empty lighter, give it electrical shots with yet again an empty lighter , hit it with a hammer and heat it till it ignites.

 

I'll post the results

Edited October 23, 2014 by modelrocket

[Ubehage]

If the R-candy goes darker, it means that you are using too much heat. I'm not sure about the exact temps, but I think sugar will caramellize at 132C.

At this temperature, there is no problem regarding safety. But you are actually degrading your fuel. It will work much better, if the sugar is all melted; but not darkened.

[modelrocket]

If the R-candy goes darker, it means that you are using too much heat. I'm not sure about the exact temps, but I think sugar will caramellize at 132C.

At this temperature, there is no problem regarding safety. But you are actually degrading your fuel. It will work much better, if the sugar is all melted; but not darkened.

which is like impossible i think

Edited October 24, 2014 by modelrocket

[Ubehage]

Not at all. You just need to control the temp. I use(d) an electric skillet, set to be between 105C and 120C.

And, you need to keep the mix moving. It will accumulate heat, if you leave it on the pan.

Edited October 24, 2014 by Ubehage

[modelrocket]

Not at all. You just need to control the temp. I use(d) an electric skillet, set to be between 105C and 120C.

And, you need to keep the mix moving. It will accumulate heat, if you leave it on the pan.

 

105 degrees??? how long does that take lol?

[Ubehage]

I made 1.5kg batches, and it took about 30-45 minutes.

I started by boiling the water and dissolved KNO3 and glucose at max heat.

Then turned down the heat, and added the sugar. And keep the mixture moving, and spread it out to expose as much surface in as thin a layer, as possible.

[Bobosan]

105 degrees??? how long does that take lol?

 

105 celsius = 221 fahrenheit

[stix]

As someone else mentioned it sounds like you are not using enough water.

 

When I make r-candy (dissolved/recrystallized method):

• I simply dump all the ingredients in a cold electric fry-pan/skillet
• Add enough water to ensure it's all dissolved (too much water doesn't matter - it just takes longer)
• Leave on medium heat (approx. 60C) and stir until there are no granules
• Slowly turn the heat up (over 3-5min period) to around 100C for maximum evaporation to occur
• Keep stirring until I get to the 'mashed potato' stage (sometimes 10mins - see point 2)
• Turn up to approx. 140-150C and keep stirring but more vigorously
• When most of the water has been driven off, I do a 'snap test' and keep doing so until I'm satisfied
• I then turn the heat down to around 120C and cast before it gets too cold

I've always found this method more time consuming and inconsistent due to not really being able to determine properly if all the water has been driven off.

 

I now use the 'melted' method and powder up my KNO3 with a coffee grinder - much easier I think.

 

Anyway, there are various methods to making r-candy and various motor configurations, so to each their own.

 

Cheers.

Edited October 26, 2014 by stix

[Ubehage]

I've always found this method more time consuming and inconsistent due to not really being able to determine properly if all the water has been driven off.

Take a small piece aside, and let it cool off. Then break it. If it snaps, then it's dry.

If it's not all dried out, it will bend and crumble. But if it's all dried, it will quickly turn into rock-hard candy.

[stix]

Take a small piece aside, and let it cool off. Then break it. If it snaps, then it's dry.

If it's not all dried out, it will bend and crumble. But if it's all dried, it will quickly turn into rock-hard candy.

 

Yeah thanks Ubehage. I am well aware of that, having done it dozens of times with great results

 

The point I was trying to make is that the 'snap test' is still not good enough because it will 'snap' even with moisture in it - how much is difficult to say, but it does affect the burn rate which is important to know in model rocketry but perhaps not so much in fireworks skyrockets etc... dunno.

 

I don't really want to have a debate about it, but...

 

Not having a ball mill to powder my KNO3, I was always a great promoter of the dissolved/recrystallized method, but after investing $30 in a coffee grinder, I have never looked back. I now prefer the 'melted method'.

 

Gone are the days of panicking about the consistency of "mashed potatoes, topped with grated cheese, sour cream and chives with a light sprinkling of cracked peppercorns"... Now I'm just happy with instant potato - Melt, Mix and Done.

 

Actually, I think I was meant to be talking about caramel candy toffee? - anyway, got my recipes mixed up

 

Cheers.

Edited October 27, 2014 by stix

[yoyo]

Is the melted method just 2 parts oxidizer and 1 part fuel, no water? If you use really pure KNO3 and sugar do you avoid caramelization, or just counter it with iron oxide?

[pyroman2498]

why don't you guys add corn syrup, its the binder for this mix , I hear people are getting a much more consistent burn rate and the fuel isn't as crumbly.

As for why cast it rather than ram it? that's an easy one I can spend 100$ and make 15 or so K engines , and not have to get a press and special custom tooling to press it .

 

Stay Safe and Stay Green

 

~Steven