More uses for coal

[BikiniViking]

I'm finding that while attempting to mass-produce tar for things like roofs and ship repair, we're creating an abundance of coal that is lower quality than we'd normally use in our smelting/furnaces/etc. Would be nice to be able to use this material into something useful.

Some ideas I have floating around in my brain:

As a paving stone
In painting as a pigment (grind on a quern and mix to form a pigment, or grind coal + wax/candleberry = charcoal)
Water purification to grant an increase in Q to water (grind on a quern, add the use of a demijohn, and water. Might need the addition of some kind of filter?; higher Q = higher bonus to water).
Coal figurine as a gilding (buff to masonry or mining, perhaps?) - higher Q = higher bonus
Offering to Shubin (a Slavic mining spirit). This would probably require a larger amount of coal and some sort of binding agent such as wax, or bone glue. By creating this one could theoretically provide a buff to one's mining skill for a certain number of hours? This one is a bit of an out there idea, but thought it could be cool.

[Darruin]

I'm finding that while attempting to mass-produce tar for things like roofs and ship repair, we're creating an abundance of coal that is lower quality than we'd normally use in our smelting/furnaces/etc.

I think that's exactly what the problem is, tar kilns should give more tar.