With the many attempts I've had at filling all the little holes that have developed in the old silent burners of the Optimus 182 I found that inadvertently I've removed the carbon deposits the old fashioned way. All most exactly as described in the old text on this excellent site.

I think with all the heating and plunging into pickling acid the little holes have been un-bunged from ages of carbon. After every pickling I flushed out the carbon with water - got some big chunks out too.

Dave.

Just out of interest, what were you pickling with?

A Citric acid solution.

Dave.

I followed Daves route for carbon removal.
I soaked the burner in citric acid o/night then heated it to red heat & plunged it back into the acid. By tapping the tubes & simultaneously turning the burner surprising amounts of 5h can be made to come out. How to stop it forming? Hmmm!

I was wondering, whether acid would eat up copper burner head--not being a metallugist, I am ignorant. Some burners are made of brass, but some are copper. Have you noticed any reaction of copper to the acid bath?

I am hesitant to find out, and I use carburator cleaner. I fill the burner up with it and leave the burner for a while, and it dissolves the carbon deposit inside. Then I use pipe cleaner (cotton with embedded copper wire) to clean the inside as far as it will go. Then I flush with water. I may then additionally treat it with heat, in order to burn off any residue.

My very good friend Henry has a most effective way of removing carbon deposits from the inside of burner heads. He removes the burner head from the riser/spirit cup and then removes the jet. Using an oxy-acetylene torch he then heats the burner to a dull red. [The squeamish should now look away]. He then shuts off the acetylene to the torch and GENTLY directs a jet of oxygen into the base of the burner. This must be done with extreme care since the carbon now burning in the oxygen stream inside the burner head generates plenty of heat and could damage the burner. He adjusts the oxygen flow to keep the carbon burning but the burner head not too hot. Plenty of debri gets blown out of the hole where the jet nomally resides so protective clothing, goggles etc. should be worn.
I should stress that I have not done this or indeed seen it yet but will hopefully when Henry returns from his lamp and stove collecting trip to Crete (not sure his missus is aware of this aspect of the trip!).
I'm sure Henry won't mind me sharing this on the forum in his absence BUT PLEASE TAKE CARE IF YOU DECIDE TO TRY THIS.

Colin.

As I remember from chemistry lessons, copper doesn't react too strongly with most acids except nitric. Citric acid is a weak organic acid pretty much like vinegar - which given time will form verdigris - but slowly. There might be a risk to the zinc component in surface layer of the brass - anyone know? but I haven't seen any noticeable degradation from soaking burners in citric acid for up to 24 hours

There need be no worries about corroding copper or or brass when pickling with citric acid solution. And the acid is safe - even if a little bitter tasting. Only a short pickle is needed after quenching to remove flux. A long pickle (24hrs) will result in all the oxidation being removed leaving copper a lovely salmon pink - after scrubbing in water. That's how it worked out with my small steam engine boiler. It's now oxidised nicely looking grubby again.

For the carbon removal I believe it wasn't the acid, just the heating to dull / medium red heat then quenching when it had just cooled to black again.

Dave.

If you look at past threads way back It was me that sergested citric acid as a cleaner.
I have used this methed of cleaning for years now long before I came to this forum. The only time this has ever created a problem is when the burner tubes has holes in it. With it removeing the carbon the holes leak. This is not the cause of citric.
The citric works better at room tempriture if the soluteion is cold it hardly does anything.
I normaly clean nickeled tanks etc with it as well, no problems here.
Yes if you let it soak in this for too long the brass goes pink like copper. But so does any acid bath I think vinegar will do the same as well, although I have not tried to get this look.
After cleaning with citric and rincing it off I dip it into a bath of Bi-carb soda (baking soda. I also use this to kill the acid on automotive battery termanles, mixed with water. This will kill any acid that remains.
I do not recomend you to consume this after you have cleaned yor stove. The carbon may cause side affects But the citric should not harm you.
Albert