Clay Pipes

Clay pipes were also a product of several of the brick companies in Oakleigh.  These pipes came in several sizes and patterns from large diameter sewage pipes down to small diameter agricultural (aggie) pipes used for drainage.  Other pipes were T or Y branch, along with numerous other shapes.  As well as pipes, chimney pots and flue linings were also made.  These days, there is a market for reproduction pieces used to renovate period homes.  Many pipes have a beveled end to fit the end of another pipe.

There were two types of pipe; salt glazed pipe and salt glazed vitrified pipe, that is, a pipe that is non-porous after firing.  Salt was thrown into the kiln as pipes were being fired.  The resulting salt steam vapour coated the surface of the pipe.  Vitrification is the process where firing causes the glaze to fuse, bonding crystalline grains to each other and the clay. Sometimes slip glazing was also done, usually on pipes that would be porous after firing.  These glazes were composed of manganese peroxide, feldspar or limestone.  Salt glazing of pipes fired in tunnel kilns was difficult.

Glazing is done on the whole pipe, both internal and external.  This is done not only for porosity, but also to aid flow and reduce resistance through the pipes and also to resist any chemical action.  Next came the firing.  These days, smaller pipes are put inside larger ones to reduce space used in the kiln.  At the time of the Oakleigh works, techniques were not sufficiently advanced to allow this.  Pipes were fired for anything up to 24 hours.

Clay pipes were restricted in length because of the gravity process.  Most were 3 feet long (just under 1 metre).  In the 1970s plastic pipes became popular and the days of clay pipes were numbered.  But under most cites of the world, hundreds, sometimes thousands of miles of clay pipes continue to give excellent service die to their non-corrosive coatings.