[MOTB2021]

There is no soot from burning alcohol & has negligible emissions. Chances are if you are seeing soot, it is from using 70% alcohol, meaning the 30% left has impurities. There is also another possibility, being the thin metal heating up is causing some soot from the paint on the can vaporizing. Try using sandpaper and remove the paint from top of your penny stove.

The can I was using was a tin can that originally contained food. It didn't have any paint on it. I also made sure to take the paper label off first. What I'm referring to as soot is the black stuff that forms on the bottom. I'm assuming that is sort.

 

[Spenser]

that may be cause you are using 70 proof then impurities in the remaining m30 %

 

[MOTB2021]

that may be cause you are using 70 proof then impurities in the remaining m30 %

But the soot doesn't come from the alcohol directly, correct? I guess I just don't understand why soot forms on the can as a result of using 70%, but there would be no soot put into the air if I were not burning the alcohol directly under a container. This would seem to indicate that soot forms as the result of an interaction between the flame and the metal.

 

[Spenser]

the container catches it so to speak, without the container the soot travels aimlessly without a concentration attaching to something that you can actually see. Think of 1/4 cup of sand in front of a big fan, the sand will scatter with small particles vs. a clump of sand, to the eye the sand disappears, but in reality it is just too small to see unless it is all clumped together.

So in short, soot is present without pot on top of stove, just not confined to one area so you do not notice it.

 

[MOTB2021]

the container catches it so to speak, without the container the soot travels aimlessly without a concentration attaching to something that you can actually see. Think of 1/4 cup of sand in front of a big fan, the sand will scatter with small particles vs. a clump of sand, to the eye the sand disappears, but in reality it is just too small to see unless it is all clumped together.

So in short, soot is present without pot on top of stove, just not confined to one area so you do not notice it.

Which means it's still in the air to be breathed in by anyone in the room. That doesn't sound good. So would having something over the flame, even if not for the purpose of heating something up, still be beneficial in the way that it captures a good amount of the soot before it goes out into the air? Seems that it would be better that way than to let it be breathable.
I guess I'll have to stock up on denatured alcohol if I want to use it in an indoor emergency. I started with 70% isopropyl because of the paint can/toilet paper alcohol heaters I saw on Youtube, and then decided to try variations of that, and trying to use them as stoves.

One interesting experience I had is in using a plastic scoop, like the kind you can find in protein powder tubs. They can hold up to 2oz. of liquid. But I stuffed one with cotton balls, then poured 1oz. of 70% alcohol into it to use as a stove. I also lined the top part of it with aluminum foil to keep it from catching on fire (I couldn't find anything else this small that wasn't plastic). The first big surprise is that it didn't even melt the plastic at all. The second surprise is that the alcohol burned for a whole 22 minutes! When I tried the same thing with a 15oz size can, it burned for only 8 minutes. When I used a small pie tin with no "wick", it burned for just 6 minutes. Granted, the water I was heating with the "scoop" version took longer to get boiling. It took 9 minutes as opposed to 4 1/2 minutes with the pie tin. Much less soot though.

 

[MOTB2021]

EDIT

 

[Spenser]

boils down to surface area. Pour 2 cups into a huge pan and light, it will go out fast, aS the surface area is huge so entire top surface is burning vapor.

 

[MOTB2021]

boils down to surface area. Pour 2 cups into a huge pan and light, it will go out fast, aS the surface area is huge so entire top surface is burning vapor.

Sounds like the smaller the surface area, the better--both in burn time and soot production. I think for my next experiment, I'm going to make on of the jar candle set-ups where a hole is punched into the metal lid of a glass jar and a wick is fed through it to burn alcohol in the jar. The neat thing with this way is that a similar lid with no hole could then be used to seal up the unused alcohol for later use. It's also easy to see how much is left. Like this one:

 

[Spenser]

add some food dye to increase brightness, will add some color to the flames. Not too much light emits from alcohol lamps lumen wise.

 

[MOTB2021]

could you try testing this using 90% alcohol and see if it works, as that looks fine to me

This is my response to what you asked me back on February 5th. I finally got some 91% isopropyl alcohol and tried it in my penny stove. Once again, it didn't work. I gave it several valiant attempts, but the results were exactly the same as when I did it with 70%. I think I'll stick with the candle jar design. I've been having a lot of success with that.

 

[NMPRN]

Of course, go with what your happy with. But test the candle jar method in the real world before you write off much more efficient ways to turn fuel into heat.

If the bottom of your cooking pot is turning black your wasting fuel and putting a bunch of gunk in the air. (...soot is just the byproduct of incomplete combustion of the alcohol)

 

[MOTB2021]

Of course, go with what your happy with. But test the candle jar method in the real world before you write off much more efficient ways to turn fuel into heat.

If the bottom of your cooking pot is turning black your wasting fuel and putting a bunch of gunk in the air. (...soot is just the byproduct of incomplete combustion of the alcohol)

Doing testing is what I have been doing. I have been heating water using the candle jar method many times. It does put a lot of soot on the bottom of the can, but only when I use 91% for some reason. It never happens when I use 70%. I have been curious as to why that's the case. The time it takes for the water to boil is about the same whether I use 91% or 70%. Given a choice between these two, it seems like using 70% is the better choice in order to avoid the soot buildup. What do you think?

 

[MOTB2021]

What methods are there to burn 91% Isopropyl alcohol without producing soot? Would it help to dilute it somewhat with water first? I ask that because I've had good luck in getting 70% to not produce soot, and the only difference I know of between them is the higher water content. So, would it help to add water to 91%, to dilute it down to maybe 80% alcohol?

 

[NMPRN]

What methods are there to burn 91% Isopropyl alcohol without producing soot?

The method I'd use is to work on your stove design. My stoves burn 91% with nice blue flames and don't have a soot problem.

 

[Kauboy]

It all comes down to proper air/fuel mix.
Soot is a result of an incomplete burn. Either too much fuel, or not enough O2. Smaller holes may yield a better burn.

 

[MOTB2021]

The method I'd use is to work on your stove design. My stoves burn 91% with nice blue flames and don't have a soot problem.

I posted a pic of mine in post #15, and again in #17 (second item). What would you suggest I change in my design?

 

[MOTB2021]

It all comes down to proper air/fuel mix.
Soot is a result of an incomplete burn. Either too much fuel, or not enough O2. Smaller holes may yield a better burn.

The "candle" method I've been using has a very small wick at only 1/2" exposed and using 91%. When I started out with 70%, I started with a wick length that long, but it took around 25 minutes to get the water boiling. I lengthened the wick to 3/4", and that got the boil time down to 12 minutes. No soot.
But with 91%, I keep the wick to 1/2" (after trying 3/4" and getting a huge amount of soot), and the boil time is the same 12 minutes, and yet I still get soot. What adjustment could I make to that? It seems that the problem started when going to 91%. Is there a way to increase O2 to an alcohol candle design?
I'll post a pic of what I'm using later after I get a pic taken.

BTW, in doing a little more research, I've been discovering that Isopropyl alcohol is supposedly NOT safe to use indoors! That's a shame since I've done all my experiments with it indoors, including burning 10oz. in a "heater can" for over an hour and a half. I keep hearing from some sources that it's clean and perfectly safe. But check this out:

"No, you should not burn isopropyl alcohol indoors. Isopropyl alcohol is highly flammable and produces hazardous fumes when burned, so it should be used in well-ventilated areas only. Additionally, while isopropyl alcohol is a relatively safe chemical, the vapors and fumes it produces when burned are hazardous, so you should never breathe them in." Can I burn isopropyl alcohol indoors?

What should I make of this?

 

[Kauboy]

I have no direct experience with alcohol candles. I just know the basic principles of combustion that are always true. Fuel, oxygen, fire. The fire is easy. The fuel/air ratio is the trick.
You need to find the right ratio, and the only real thing you can control is the fuel input. Reduce the hole size and see if restricting the fuel gives you a better burn.

Isopropyl alcohol is literally 3 elements, carbon, oxygen, and hydrogen. The combination of additional oxygen in a combustion reaction will only yield molecular combinations of these elements.
The worst thing you'll get out of this is carbon monoxide from an incomplete burn, and the amounts are extremely low. Small iso stoves are safe to use an any ventilated open space, including indoors.

 

[MOTB2021]

I have no direct experience with alcohol candles. I just know the basic principles of combustion that are always true. Fuel, oxygen, fire. The fire is easy. The fuel/air ratio is the trick.
You need to find the right ratio, and the only real thing you can control is the fuel input. Reduce the hole size and see if restricting the fuel gives you a better burn.

Isopropyl alcohol is literally 3 elements, carbon, oxygen, and hydrogen. The combination of additional oxygen in a combustion reaction will only yield molecular combinations of these elements.
The worst thing you'll get out of this is carbon monoxide from an incomplete burn, and the amounts are extremely low. Small iso stoves are safe to use an any ventilated open space, including indoors.

Well, I seem to have the hole size down to a bare minimum, but I still get a pretty high flame.
As promised, here is a pic of what I've made. They are plastic pill bottles. I pried out the inner cap from the safety cap, punched a hole in the middle, and then inserted an aluminum tube made from a small strip cut from an aluminum can. That's to make sure the fire is only in contact with metal, and not plastic. I've actually only used the one on the right. What do you think of these?

 

[Kauboy]

Well, I seem to have the hole size down to a bare minimum, but I still get a pretty high flame.
As promised, here is a pic of what I've made. They are plastic pill bottles. I pried out the inner cap from the safety cap, punched a hole in the middle, and then inserted an aluminum tube made from a small strip cut from an aluminum can. That's to make sure the fire is only in contact with metal, and not plastic. I've actually only used the one on the right. What do you think of these?

What do you consider to be "bare minimum" for your stove hole size?
Are you getting a blue flame, or yellow? Those alcohol stoves should produce a hot blue flame when the combustion is optimal. If you're getting yellow, your fuel/air ratio is too rich.

Your candles look fine. I'd be worried about the thinner ones tipping over, but that just means a bit more precaution when using them.
I assume they're burning just fine, and you would expect a yellow flame since they use a wick which introduces a minor amount of contaminants into the mix.