Enter the Toning

[hotwheelsearl]

Several months ago, I bought this siliqua of Constantius II. It came relatively white, with some standard blackish toning.

 

Flash forward a few months, after leaving it on my desk the whole time...

Now I've got this lovely blue and gold edge toning. Wow, I did not think that 1,600 year old coins would tone in 4 months, but here we are. Stupendous!

[shanxi]

8 hours ago, hotwheelsearl said:

Wow, I did not think that 1,600 year old coins would tone in 4 months,

These colours are the result of wave interference with visible light. For this, the layer thickness must be in the range of 100 to 200nm. Thicker or thinner layers do not show any colours.

Now 100nm is almost nothing, 100nm is only 0.0001mm. Such an oxidation layer is formed quickly.

Unfortunately the colours disappear as the layer gets thicker.

 

Here is one of mine:

Julius Caesar
AR Denarius, 46/45 BC
Military mint travelling with Caesar in Spain
Obv.: Diademed head of Venus right, Cupid behind shoulder
Rev.: Trophy with oval shields between female and male seated captives, CAESAR in exergue
Ag, 3.90g, 18mm
Ref.: BMC 89, Crawf. 468/1, Syd. 1014

Edited April 9, 2023 by shanxi

[Roman Collector]

This one had some colorful toning for a while. It's a gunmetal gray now.

[Victrix]

You guys have some cool toned coins! I don’t have many with it, so I’ll just share my Mark Antony denarius that over time is getting some cool colours 😀

[Edessa]

Roman Republic. L. Appuleius Saturninus. 104 BC. AR Denarius (19mm, 3.81g, 6h). Obv: Helmeted head of Roma left. Rev: Saturn in quadriga right, holding reins and harpa; above, •C• (control-mark); L• SATVRN in exergue. Ref: Appuleia 1; Syd 578; Craw 317/3a. 

[robinjojo]

19 hours ago, hotwheelsearl said:

Several months ago, I bought this siliqua of Constantius II. It came relatively white, with some standard blackish toning.

 

Flash forward a few months, after leaving it on my desk the whole time...

Now I've got this lovely blue and gold edge toning. Wow, I did not think that 1,600 year old coins would tone in 4 months, but here we are. Stupendous!

Nice toning!  My experience is that toning can happen quite rapidly, depending on humidity, and other chemicals (notably sulfur) that might be present in the air or on the surface where the coin resides.  Silver and bronze are quite reactive and color can change without the need of the ages.  If you like the color of the coin, and it is very nice, you might consider storing it in a safety flip.  It might darken a bit but largely remain the same.

My ancient with a colorful toning took over 40 years to reach its current state.  The coin has some minor horn silver, and I think over the years it had a benign affect on the coin, giving it the multi-hued toning that now graces it.  For almost all of the 40 years the coin was stored in a cotton lined envelope.  I don't think the cotton had an affect on the toning as I have other silver coins stored in similar envelopes, mostly unchanged over the years.

 

Edited April 9, 2023 by robinjojo