Tempering colours lifespan

[Joel OF]

I watched a programme about Tudor armourers a while back and I'm sure I remember the programme saying that for Queen Elizabeth's armour the armourers tempered it to an iridescent blue for effect, however over time the temper colours have faded.
The blues and purples in tempering are lovely and seem like a nice way to finish some pieces.
I bet I'm about to open Pandora's Box but what factors are involved in how long temper colours last and how can you preserve them?

[Chinobi]

temper colors are governed by the thickness of the oxide layer on the surface of the metal.  as the metal ages it continues to oxidize (significantly slower at room temp, almost in real time at higher temperatures, allowing us to use it as a rough thermometer), altering the patina's appearance over time.  this can be halted by applying a surface finish such as renaissance wax, bees wax, shellac, varnish, clearcoat or any number of other surface finishes (see the alchemy subforum, there are several good discussions with recipes over there).

 

however: the application of such a surface coat WILL by itself alter the appearance of the patina, so be prepared for that and make yourself a sample blank of the same materials to see exactly how much it will shift.

[Thomas Dean]

I have pieces that are at least 8yrs old with the colors remaining,  finished with a spray polyurethane (Krylon), or wax. But a word of caution with copper. ANY finish will remove the beautiful colors that you get when you heat the copper==blues, purples, reds, gold, green, etc. ==They are gone the instant the finish hits the metal.

[WayneCoeArtistBlacksmith]

I have a vanity stool that I made over 10 years ago with Kudzu leaves that got heat colored (temper colored, though I feel that temper is not a correct term because tempering is the drawing down of the brittle hardness to toughness after hardening.  Since my piece was never hardened I choose to call it "heat coloring" ) to straw and blue.  I waxed the piece back then.  It sits in our bathroom and still has the colors.

[Frank Turley]

A mentor, Victor Vera, was brought up in a smithy in San Luis Potosi, Mexico. He said that in the early 1900's, his dad and uncle would heat-color their bare-metal lock plates and keys by burying them in the heated sand of a metal sand box. The articles were forge heated until blue and then oil quenched. The oil darkened the blue a little, but Victor claimed that it was fairly long lasting.

 

Sayings and Cornpone

"Yep kids, that is the true source of shredded coconut."

      Frank Turley to kids watching the result of rasping a horse's white hoof.

[JNewman]

I had a really interesting thing happen with oxide colours on a bowl a few years ago.  I used a torch on a bowl I made as a wedding present to get some great purples blues and bronze colours.  I put a thin coat of linseed oil on it to protect it and all the colours disappeared.   I panicked a little as the wedding was in a day or two and I did not have time to make or buy anything else,  and the bowl was pretty plain looking without the colours.   I thought about it for a little while and then used some lacquer thinner to remove the oil.  All the colours reappeared.  A coat of spray lacquer did not affect the colours when i sprayed it on.

[Joel OF]

Newan, what sort of lacquer was that? I asked a similar question aged ago about preserving rust colours & someone said to use a spray from Halfords (UK car parts shop), wondering if your lacquer & his spray is the same thing...

[JNewman]

I cannot remember the exact brand just one from the hardware store.