Main Discussion Area > Primitive Skills

clay and oil on fire - porosity

(1/3) > >>

GlisGlis:
my second try with self refined clay.
I had some left from first try and wanted to make an oil lamp vaguely based on the Lucerne (etrurian or roman)
I did not use a mould and the shape is very freely influenced tough.
tha lamp survived firing in an old stove (no idea of the temperature reached)and has been lit and  burning for 2 hours (cotton wick and used frying oil)
the problem is the object is pretty porous. once left a night long full of oil the oil soaked the clay making a thin patina on the outside. It is still usable but is not nice to see or handle
Is that caused by the crudely refined clay or by the low cooking temperatures? or both?
Self made clay is indeed a great toy. Now thinking to make an ocarina.

nclonghunter:
Interesting and cool idea....I can not answer the firing question but if it "rang" when tapped after firing then it was well fired. In pots that are going to be cooked in or that hold water the inside is burnished with a smooth stone or polished antler. This aligns the clay and compacts the molecules making it way less porous. May be hard to do with a oil lamp and the small openings. My next thought would be to heat the clay and pour in a beeswax to coat and line the inside. If it only burns at the spout then the remaining insides portion should stay cool and the wax coating intact thus preventing it from leaching through the lamp. If you try it, let us know....

Pat B:
I'm not sure but I'd think you'd need a glaze to make the clay nonporous. You could seal it with pitch or beeswax to help keep the oil from sinking in.

DC:
Low fired clay(terracotta) is porous. I'm not sure if different clays have different porosities. High fired are(ironware) are basically glass and are watertight. I think that some clay will not take high fire but someone else will know that. For example, the clays around here will make good terracotta but if you try to high fire them they just melt or burn kinda. 

Zuma:
One way you can test your future lamp would
 be to fill it with water and see if it bleeds through.
It will dry and then you could seal it like others have said.
Native Americans used the porosity to cause evaporation
that cooled the water in the pot. The higher the firing temp
the tighter the material becomes. (shrinkage??)
Zuma

Navigation

[0] Message Index

[#] Next page