Manganese or Cobalt will work for black. Heavy amounts of Cobalt give a very black colour with overtones of blue in a firing... again oxidation firing.
I can look up reduction firing (which are more normative for brick) colours once I am home this evening. Reduction firings tend to give either more earthy tones or in some cases more metalic tones. According to my pottery instructor (who's done a fair amount of reduction work) more then 2% iron oxides in reduction fired bricks will make them very brittle. Copper in reduction fires is red or red violet Iron tends to be black or a greeny black colour - responsible for the colour in Celadon glazes. Green in reduction fires is very very uncommon - requires high amounts of barium Manganese is brown Cobalt is blue - violet Copper and cobalt mixed gives wine red to a red hued purple My experience with reduction fires (which is admitably limited, and all were done using pre-industrial techniques) is that the colouring is never entirely uniform. Flashing occurs with pit fires (which are vaguely like firing a brick works but different). Since you don't have uniform heating in either of these types of firings you get some spots in the pile of bricks (or pottery) that are at different temperatures or have more or less oxygen getting to them; so the results are highly erratic (and IMO more interesting). Modern methods have strived to make these things much more uniform - and have for the most part succeeded... which means more stable bricks - but colour wise also more uniform. For those who have never seen brick fired - in pre-industrial times folks basically make a bunch of bricks stack them in large pile with holes at the bottom to put fuel... I think of it as building the bricks around a fuel pile. Then light the works - the pile of bricks you are firing act as both kiln and object being fired. The most uniform (and traditionally the most expensive) brick would have been those that were in the center of the pile of bricks. So more expensive brick is both more stable (ie doesn't break or crumble easily) and more uniform in look. Which if you are running a campaign that could be a subtle hint about the relative wealth of the person who made the building or wall. -Sue --- On Tue, 11/2/10, Nigel McCarty-Eigenmann <[email protected]> wrote: > From: Nigel McCarty-Eigenmann <[email protected]> > Subject: RE: [gurps] A question about Bricks > To: "'The GURPSnet mailing list'" <[email protected]> > Received: Tuesday, November 2, 2010, 11:35 AM > What I am looking for is some > regional definition for some cities in a > fantasy setting I am currently hammering into shape. > > My base city for the setting has brick yards out side of > its walls, where > they raised the battalions of infantry and the starting > seeds for > republicanism came about > > The sign of four bricks is the ministerial sigil that looks > after bricks, > the building industry, and the army. > > Since the region is known to have iron bearing sands, so I > am mooting Red > Brick for the city, but I would like to have black, as > black would suit the > religious iconography I have got up and running. > > ... I could handwave a bit and say its manganese oxide and > call the bricks > black even though they are actually dark brown? That > also allows the > Damascus steel from the uplands tribes I wanted... > > [Green Brick is for the Lakeland towns where good brasses > are made, and > copper and tin mines abound] > > ...so Ta Sue :) > > McE > > > -----Original Message----- > > From: [email protected] > [mailto:gurpsnet-l- > > [email protected]] > On Behalf Of Susan Koziel > > Sent: 02 November 2010 16:46 > > To: The GURPSnet mailing list > > Subject: Re: [gurps] A question about Bricks > > > > Not brick making but pottery/glazing... which has some > of the same colour > > effects (depending on if the bricks are fired under > oxidizing or reducing > > conditions... the colours I'm listing are for > oxidizing conditions. I am > > not sure of reducing condition colours - I do not do > enough reduction > > firings to know what colours the various oxides give. > > > > Cobat oxide - blue > > Iron oxide - red > > Copper oxide - green > > Manganese oxide - brown > > > > Granted these colours are based on the fact that the > clay body you are > > using for the bricks is white or grey and not black or > red. > > Red and some of the black clays fire to a red colour > so mixing oxides with > > them just tends to give muddy versions of the colour > of the oxides. > > > > Different combinations of minerals will give you > different colours due to > > chemical reactions... so it doesn't work like a > painting where you can mix > > colours - sure you can mix the colours but blue > (cobalt) and red (iron) do > > not give purple... it acutally gives a sort of goldish > colour or a muddy > > brown - depending on proportions of the mix. > > > > Often time the colour of bricks has to do with the > local clay they made > > the brick from - typically brick is made from the > cheapest local clay > > deposit. So the colour is more a consequence of which > of the brick works > > you get the brick from. > > > > The exception to this is the brick that is made into > high temperature > > brick - where they take high quality clays and have > specific recipes that > > allow the brick to survive high temps or exotic > chemical conditions. > > Fire brick is pretty much a uniform yellow/beige > colour. > > > > -Sue > > > > --- On Tue, 11/2/10, nigel mccarty-eigenmann <[email protected]> > > wrote: > > > > > From: nigel mccarty-eigenmann <[email protected]> > > > Subject: [gurps] A question about Bricks > > > To: "Gurps" <[email protected]> > > > Received: Tuesday, November 2, 2010, 6:22 AM > > > Dear Groupmind, > > > > > > Anyone know about brickmaking? > > > > > > What mineral contents would make a brick come out > of the > > > oven blue, green > > > and black? > > > > > > > > > McE > > > > > > > > > _______________________________________________ > > > GurpsNet-L mailing list <[email protected]> > > > http://mail.sjgames.com/mailman/listinfo/gurpsnet-l > > > > > _______________________________________________ > > GurpsNet-L mailing list <[email protected]> > > http://mail.sjgames.com/mailman/listinfo/gurpsnet-l > > _______________________________________________ > GurpsNet-L mailing list <[email protected]> > http://mail.sjgames.com/mailman/listinfo/gurpsnet-l > _______________________________________________ GurpsNet-L mailing list <[email protected]> http://mail.sjgames.com/mailman/listinfo/gurpsnet-l
