That gold is just absolutely beautiful.
What in the heck does the fire of our torch have to do with the chemistry of metals or moving electrons?
what part of my torch is hotter?
How can I better understand what my torch or burner does to my metal or to a salt of my metal?
I cannot explain this well in typing or writing, how can I do it better?
Different parts of the flame coming from your torch tip or furnace burner will have different properties.
Oxidation (lose of electrons)
Reduction (Gain of electrons)
Oxidizing (ability to take electrons)
Reducing (ability to give electrons)
Many torches or burners can be tuned or adjusted, adjusting an oxidizer fuel ratio, and thus these different properties. Normally propane or a Mapp-gas torch are normally tuned in their construction of fuel/air ratio and non adjustable, and will hold that tuning as long as the torch head is clean and not mechanically damaged (from corrosion or other).
The yellow portion of the flame is cold in comparison, just in front of the very tip of a blue cone is the hottest part of the flame.
the yellow flame is a reducing agent for metals, If the torch is sooty and smokey it is also producing another reducing agent, carbon, to the mix.
The blue cone of the torches flame has an excess of air or oxygen, an oxidizing flame, also meaning it can take electrons from metals that are fairly easy to oxidize or metals which are more reactive. this portion of the flame can oxidize a metal (take iron for example making a salt of that metal or rust, iron oxides or take electron from copper to form copper oxides.
Gold is not very reactive at all even in most melts, gold cannot be easily oxidized, chloride salts are one flux that can oxidize gold in a molten state.
Just as excess oxygen in a melt can more easily take electrons from a more reactive metal in a melt to form metal oxides, and just as carbon can reduce metal ions in a melt converting say copper oxide to copper metal.
In welding we often use flux to help offset this oxidation process of our torch or welding environment, basically controlling the oxidation reduction of the welding environment to give us a good bond or bead (which may also be formed as different allow of the two metals we are bonding or the welded area may even have a different crystalline structure, but this can also be somewhat from the alloying but more from the heating and cooling process of the metal which is a factor of forming the crystal structure of the metal the bead or even the metal around the weld that we have changed the crystal structure of in our welding process.
Such as of smaller more densely packed crystal structure and thus a harder metal structure but more brittle and easier to break, or of the softer larger crystals more loosely packed that help the metal bend or be more malleable or easy to bend or stretch easy.
I did not want to get into welding but if we do a little it can give us a better idea of what is going on.
Gold will also have a crystal structure ( not considering alloying here), and this structure can be changed mechanically by working the gold, rolling, hammering bending...(gold or copper are also different than iron in how the metal is hardened or softened or how we change the crystal structure of the different metals).
Gold can be hardened under a hammer, or by bending, as you smash the metal or bend the joint you are changing the crystal structure making it harder more brittle easier to crack under more work, harder to stretch of change its form.
We can rearrange or change the crystals to make the gold soft again by heating it to red hot in a re-crystallization process as we get the gold atoms excited or moving around. Pure gold can be dipped in water for cooling and further annealing, while other alloys of gold (like with nickle) cooling may be done differently such as cooling slower on a cool metal plate, Nick being a jeweler will know more about how gold alloys react to heat treatment, my skill is more in the field of blacksmith so I understand iron better than gold.
The yellow portion of the flame is lower in oxygen, richer in fuel, and thus a reducing flame, or saying it another way, it can give electrons to metal oxides or salts of metals, as the oxide ion portion of the metal/oxide ionic compound and carbon (from burning of the fuel burn) (to produce carbon monoxide, water and excess carbon), basically, the black smoke (incomplete combustion) where even the excess carbon in the exhaust gases of your torch can become a flus to help produce a chemical reaction, the flames smoke can act as a flux or a reducing agent in a melt of metals again giving electrons to the metals ions.
As the metal oxide or salt can be reduced to molten metal or as the metal ions gain electrons to form metal atoms or an elemental metal, For example in a reducing environment we can change copper oxide (a salt of copper) to copper metal.
An oxidizing flame or environment can take electrons from the copper atoms, making a salt of copper or copper oxide out of our copper metals.
A reducing flame or environment can give electrons or convert copper oxides to copper metal in a melting process
An oxidizing flame, Blue flame (note the word I used), this oxidizing flame also refers to metals being melted or welded in a fusion process of two metal pieces and where we often alloy metal in our forming a welded bead in the joining two metals, and we also often use a chemical flux to clean or oxidize metal in the process (take electrons), or preform other chemical changes (or move those electrons)(as well as using our torch's oxidation or reduction properties) our flux may also have reduction properties or ability to provide electrons, so just as our torch or burner produces chemical change so does the flux or chemicals added to the melt.
I tried to proof read this several times with my bad eyesight and failing ability to write, I hope this is readable and makes some sense to you.