The interior doors of our house are birch and were originally finished in a dark color to look like mahogany. At some point, they were all painted white. I had planned on stripping and restoring all of them this winter, but it struggled to figure out how to do so without creating fumes or using chemicals.
I started by taking one of the closet doors to the garage and attacking it with a heat gun, followed by soy gel in stubborn spots. I noticed that the paint would flake offs next to where the heat was directly applied.
I realized that the paint would peel away if I passed the heat gun over it at low temperature, leaving the original finish completely intact. The process also creates no fumes and the paint itself comes off in large strips. I use Gorilla Tape to pull off any stubborn spots that the peeling process leaves behind.
My disclaimer is that this process works because the surface was originally finished and no prep work was done before the doors were painted. If the doors had been scuff sanded, this probably would not work. That said, he are the results so far.
The rings you see in the dark area are reflections in the finish that each strip leaves behind. Once I add a top coat of shellac, these will disappear.