EXPERIMENT #1 HYDRATE A: Hydrate clay prior adding it to the refractory mix ? (in progress)

Pottery sites tell that bentonite is used in glazes to keep the other components in suspension.  It shrinks too much to be used alone for use as a clay body.  Even drying also is a problem.  Clay body is what these folks call their clay.

Does mixing bentonite with Portland cement and sand change this.  I have no idea.  To find out I will be molding bricks that fit in my burnout oven.   If they don't crack or fall apart when drying I will try them in the oven to see how they stand up to the heat.

I have determined that mixing the cement and immediately adding the clay makes for a very weak brick.   To be fair the people at Back Yard Metal Casting were possibly mixing by hand which allowed the cement sufficient time to hydrate.

Earlier I made 2 brick adding the clay immediately after the other ingredients.  The original recipe states the clay should be added after the other ingredients are mixed.

At some point I am will want to refer back to these experiments.   To make that easier I will be naming them.

This experiment is HYDRATE A: 
Determine if it is better to pre hydrate the clay or add it dry.

Each time water is added it will be noted so that next time a more correct amount can be added earlier where possible.  The premise is that its better not to sneak up on the water adding it bit by bit.   With the clay you can end up adding water about as fast as the clay absorbs it.  Always fighting a stiff mixture.

I am not especially happy lining the forms with packing tape.  Lubricants will not work because I may coat these bricks with satanite  Thinking about placing a sheet of paper in the bottom of the form.

Hydrated Clay Procedure:

1.  Added 51 oz. water to the clay and let it rest over night.  
2.  Add water to the remaining ingredients with the power mixer.
3.  Allow the mixture to rest 10 minutes for cement hydration
4.  Add the clay to the mix and blend with the power mixer adding water if   needed.  
5.  Immediately place mix in forms.
6.  Scratch HC into the brick.

Dry Clay Procedure

1.  Add water to everything but the clay to get the desired consistency.
2.  Allow the mixture to rest 10 minutes for cement hydration.
3.  Add the amount of water used in the Wet Clay procedure.
4.  Add the dry clay.
5.  Mix with the power mixer adding water if needed.  Record water.
6.  Immediately place mix in forms.
7.  Scratch DC into the brick.

 I have hydrated the clay and recorded the water used.  The clay is a bit stiff but should work when mixed with the other ingredients.

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The refractory from experiment HYDRATE A is in the brick molds.  The Dry Clay Procedure was preformed about 4 hours after the wet.  The refractory made from wet clay was smoother than the dry.

In the Hydrated Clay Procedure 1.25 lbs of bentonite absorbed 5.5lbs of water and would have taken more it provided.  Equal water was added to the dry along with the clay.  Both mixes were made stiff for brick making.

It is now the next morning about 12 hours since the dry was done.   I am now thinking I should have covered then with wet towels.   The surfaces are not gray so not dry.  Moved all but 2 of the test cubes to the wet box.  AKA old food freezer with a bit of water in the bottom.


2 Weeks Later
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The bricks were removed from the wet chest and dried on a furnace vent in my office.  Both  hydrated and dry bricks were used in reassembling the Kerr 666,  

The furnace was heated to 710 degrees.   Then I cooled the furnace and removed the heating elements and bricks.   The DIY bricks are on the crumbly side but holding together.     This video is repeated in the next Kerr 666 post.  

The large block created in the 2 refractory experiment is harder than these which are still on the crumbly side.   I left these air dry and put them in the water the next day when the could be safely removed from the forms aka molds.   On the 2nd refractory experiment I covered the we mix in the mold with a wet towel earlier in the process.   But it also used 5 parts native clay and 1 part bentonite.  So I don't know that this experiment has resulted in usable information.


To be continued....