On Tue, Nov 2, 2010 at 12:46 PM, Susan Koziel <[email protected]> wrote: > 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. >
Only rarely were bricks made of the cheapest clay. Bricks are pretty demanding, and using unsuitable clay results in bricks that fail in firing, or fall apart, or are not water proof enough. If you look at map of historic brick making sites, you can get a pretty good map of the geology of suitable clay deposits. You can find places where bricks were made of unsuitable materials, because of difficulty in transporting proper bricks to the site, or just cheap bastards doing the building and not knowing what they were doing. (the University of Notre Dame has a bunch of buildings built in the 1860s and 1870s of the clay dug from a campus lake. It's not a suitable material for making bricks. The buildings require huge amounts of work to keep them from falling over. This was pure cheapness on the part of the university; perfectly good brick was available to them, they'd just have to have spent money on it.) > 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 Modern brick is all made from pretty carefully graded stuff, even plain red brick. -- David Scheidt [email protected] _______________________________________________ GurpsNet-L mailing list <[email protected]> http://mail.sjgames.com/mailman/listinfo/gurpsnet-l
