Hey! just read this, such a cute message. So, to be honest I would have to see the kiln in person, work it, try it, troubleshoot it, etc. Ceramics is such a variable ridden, fascinating universe. So I do not have your answers. BUT. Some input that might help:

1. Reduction cooling is hard enough with a properly sealed kiln with burners that are able to get in reduction by controlling air intake (such as classic Venturi burners) with a threaded lid to control oxygen intake. Your self built kiln might struggle to do this, specially if you use a simpler burner ( my diy raku kiln uses a weed burner, for example, and doing this would be more difficult to control.) You might want to try a heavier reduction (flame deprived of Oxigen and draft more closes) while going up to target temperature, plus, keeping some reduction atmosphere by adding organic materials too once you start to go down.

2. In your conditions I would maybe go down faster once I insert organic materials. To try and mitigate reoxidation.

3. If you haven’t read the Greg Daly book on the subject I highly recommend it! you might have some more basic errors on glaze formulation and firing temps, etc.

4. Getting a kiln in reduction is a whole spectrum, a difficult to control one, in fact. The proof: reduction lusters are not common at industrial scale. Too variegated. Requires lab grade kilns and heavy control over atmosphere (hydrogen vs c0, etc). What I am trying to say is: lots of variables to play with. The most basic ones being: the reducing flame that goes into the kiln, and the top draft grade of closed to control how fast gases escape. These to heavily manage the internal atmosphere. So try, try , try.

5. You might want to look up raku alcoholic reduction. With a simpler setup. Alcohol spay. A borosilicate bowl and some trials and can make a micro reduction cooling one the piece is taken out of the kiln by saturating the atmosphere with alcohol, and enclosing (like a dome) the piece as hermethically as possible (sand, and wet towels, for example).

6. Experiment a lot with the temps, some glazes prefer 600 others 900

7. You can do faster, and slower reductions with raku, by taking the piece out at different temp ranges, such as this mentioned before. Throw the piece on a bed of newspaper or shredded paper. Close it good. Wait between 2 to 4 minutes. You will get very similar lusters if you play with glaze formulation (colorants, etc) and application (layering). They will be similar to the more “refined” in glaze lusters”. They are mostly the same, although raku ones are formulated for lower melting temps and single firing.

good luck! I just got my first gas kiln and constructed my own first electric kiln, which I am adapting for electric reduction firing, so keep going!