Antique Moro Gunong

[kai]

Hello Ian,

as mentioned by Jose, most suasa also contains silver and it will be mostly silver sulphides contributing to any very dark patina.

For these non-silver black oxidized pieces, I wonder if there might be some arsenic also in the mix. Some oxides of arsenic can be very black in appearance.

At least the 2 common oxides of arsenic are white.

It's the arsenate salts with metals like iron that are blackish (cp. warangan). Metallic arsenic in an alloy is a quite different kettle of fish though and unlikely to be more than a trace contaminant...

I seem to recall that arsenic has some mystical properties in mainland SE Asia--certainly some of the Hmong who live in the Twin Cities used arsenic for medicinal purposes and I was told by members of that community that arsenic is a powerful substance in their culture.

Yes, arsenic compounds like realgar have been utilized in TCM (Traditional Chinese Medicine) for millennia and have a scientifically proven track record in modern medicine as well. However, there also are cancerogenic effects known...

Regards,
Kai

[Ian]

Thanks Kai.

Yes, it's arsenates [–AsO4(-3), etc.] not oxides of arsenic [As2O3, As2O5, etc.] that are black.

I'm not sure that silver oxidation explains the intense black oxidation that I observed on my samrit covered daab. Some time ago I was sent an old formula for samrit, and no mention was made of silver in the mixture if I recall correctly. Also, the intensity of the black color was much more than I see on silver covered pieces from the same general region--silver oxidation tends to be more grey than black.

I have another Lao daab from the 17th C with a samrit hilt that has virtually no oxidation, and I have no explanation why one would have such a dark patina and the other virtually none. Presumably it reflects different components in each sample of samrit.

[Battara]

Actually for silver the longer the oxidation the blacker it gets.

Another consideration is the copper content, because when copper is involved, then the darker the oxidation gets as well. Copper often gets the green/blue/even multi-color patinas. However, when mixed with certain metals, the patina might change depending on the metal mix. Copper/tin mixes (bronzes) may yield a green patina, but can also give a dark brown to even black patina. This black patina can also be seen on silver/copper mixes where the mix has a large percentage of copper (in fact, silver/copper mixes with large amounts of copper often patina quicker than either silver or copper by themselves! ).

Hope this is now clear as mud...........

[Ian]

Thanks Jose.

[F. de Luzon]

Thank you all for your comments! I haven't found time to have the metal tested but I'll give an update as soon as I have information.

Kind regards,

Fernando

[ACP]

Would it be possible for you to give me a summary of how you restored the gunong? I have one that barely escaped the bombing in Marawi and is just sitting inside my desk drawer. Big thanks in advance

[F. de Luzon]

Hi ACP, What's the condition of your gunong? Can you please post a picture? Thanks.

Fernando

[ACP]

Thanks for the reply, i will try to post some pics when i get back home.

[ACP]

Ill try to post the picture when I get back sir. Im currently out of town. My apologies