Few months back I have told Arthur that I’ll come back with every details of West Bengal(India) terracota pot foundation(Tubri) making technicalities. Finally I’ve succeeded. From my childhood I’ve watched competetions with this kind of terracota pot foundation and this year in Dipawali I have successfully made four of that kind. It’s really delicious.
Here goes every details of that, but I can’t take full credit of this as Bengalflair has helped me guiding a lot. So, thanks to him.
POT- Here we have some potters who make this type of special pots. This pots are made of clayee soil. These potters make some crucible which can withstand huge amount of heat. They pass down part of their knowledge in making these pots. They also do mix some amount of sand and mica( I assume) to make them more resistant.
Measurements- 4”/4”. Height 4” and diameter of widest part 4”
Pot Seasoning-Inner wall was coated with five layers. First layer was sand or dust of cast iron. Above four layers were coated with mica dust. Done with wood glue and dryed well under the Sun. I bored the nozzele to 8-10mm.
Along with this we added black powder to create more energy but do not want to speed up the reaction so use coarse KNO3, as target is to throw metal splinters to acceptable height. Personally I have used mill powder.
Iron-Mild Steel has been crushed with morter & pestle to a size of less than 1mm size. It’s very tiny in size and I chosed them with eye-balling as I have little experience of the particular size required.
Mixinng-Now 200gm of base mixture was added with 30gm of mill powder as starting point. And 50% of the total weight i.e.around 115gm of MS was added to it.Then 5ml of Methanol was sprinkled to dampen the mixture for better consolidation.
Loading-Exhaust bore was covere with masking tape and pot was half filled with composition. Then consolidated with wooden rammer and wooden dowel. Process repeated and entire mass was loaded. Then it was layered with pieces of papers anf finally jammed with clay. Again consolidated with rammer & dowel so that lower part can resist the pressure. I’ve also plugged with homemade made fuse at the exhaust boring.
Lighting-For better safety I fenced the pot with bricks before lighting.
After that-ROCK N ROLL.
Last but not Least-One can use steel or other solid casing but challange lies with using terracota pot. It goes without saying that if the pot bursts you get disqualified but even after brurning finishes the pot is checked by judges for any cracks even. That will also lead to disqualification.