Does sunlight damage shell and slate stones?

[kaimat]

I recently purchased a nice set of shell and slate stones and quickly after (due to cats) purchased a clear acrylic cover for my table goban. After finishing a game I like to leave it displayed under the cover to admire for a few hours or a couple days before playing more.

As I thought more about the idea of leaving the stones exposed to direct sunlight throughout the day (perhaps two hours) I began to worry that the stones (especially the shell) could be damaged from the exposure. Is this a real fear or am I being over-protective of my new stones?

[Bonobo]

I’m far from being knowledgeable in these things, but I’d rather expect the wood to be affected … darkening probably.

Greetings, Tom

[EdLee]

Hi kaimat,

Like Bonobo said, sunlight affects wood and probably the shell stones. Probably less on the slate.

To be on the safe side, I'd avoid any direct sunlight on any wooden surfaces, including gobans and bowls.

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[gowan]

I have a 30 year old set of keyaki (zelkova) wood bowls. When I got them they were a very light yellowish tan color and, without any direct sunlight exposure they are a beautiful honey color.

[bogiesan]

Slate is an igneous rock. Sunlight is nothing compared to what it's been through.
Shells? I don't know if anyone has ever done experiments to find out how the chemicals in the shell layers react to prolonged exposure to intense sunlight. However, consider where they came from and how long they were there. I cannot imagine sunlight having much of an effect on the calcium carbonate or the trace proteins.

wiki:
> Seashells are the exoskeletons of mollusks such as snails, clams, oysters and many others. Such shells have three distinct layers and are composed mostly of calcium carbonate with only a small quantity of protein--no more than 2 percent.

Here's on interesting article on how to start a business selling stuff made from clamshells that explains how to clean them and process them into gift times. Might give you some clues about the nature of the shells material and what it will withstand.

http://aqua.ucdavis.edu/DatabaseRoot/pdf/SHELLS.PDF

[tchan001]

I don't know how much of this applies to processed go shell stones but here is something from people who collect shells.

http://www.seashell-collector.com/begin ... oring.html

Sunlight

Even if sunlight is the best to observe shells, it causes a lot of damage to them. Of course, shells have different reaction to sunlight depending on their families. Cypraeidae, for example, is one of the most sensitive families. Their color fades fast. You have to know that all shells taken from their habitat will fade anyway. The only thing we can do is to slow the process. With some easy things to do you can consequently reduce the sunlight damages throughout the years.

[sparsely]

The shell stones should be fine, I think if they were coloured they might fade but they are white anyway. Calcium carbonate is white and sunlight won't change that.

[EdLee]

Calcium carbonate is white and sunlight won't change that.

Except they are not 100% CaCO₃ .
One of the main features of the shell stones is their grain patterns.

The shell stones should be fine, I think if they were coloured they might fade but they are white anyway.

They are not 100% white; that's the point of the different grades.