Are these cracks heat induced?

[Glen Blanchard]

This piece had been soaked in DNA for 24 hours and subsequently dried. I had not noticed these cracks during shaping. It was only after I had gone through some levels of sanding that they became noticeable. Now I am wondering if they were there the whole time and only became apparent once the piece had been sanded some or if I over heated the piece during the sanding itself. These are in the area of end grain. So did these cracks occur during drying or sanding?

285052

[Dave Paine]

I have experienced many such small cracks. I feel related to moisture loss during drying. The heat from sanding is not likely to penetrate deep. I sand at 750 rpm or less these days. I get a better result with slower sanding than faster in addition to less heat.

Sometimes the cracks only appear later, as the wood looses more moisture.

You can try thin CA glue, but if the wood has more moisture to loose, they will likely open up some more.

[Reed Gray]

Heat checks are pretty tiny, much smaller than the ones you have there. I would guess that they were in the wood to begin with. They look typical for drying cracks on the end of a log. They can be tiny, and of course, expand a bit more as the bowl starts to dry. For pieces that have been turned and then crack, usually it is one or two bigger cracks.

robo hippy

[Faust M. Ruggiero]

Glen, The cracks may have occurred during drying but showed up when you sanded. Fine paper leaves dust small enough to fill tiny cracks and scratches making them visible. If this hollow form is totally dry I think the wood is probably stable and the cracks may not grow. If you took it out of the DNA only days ago, that will be another story.
I would not glue them. I would just take my chances. If they bother you, paint this piece or texture it with pyro and hide them.
faust

[Glen Blanchard]

Thanks for the responses, gentlemen. There is little doubt in my mind that that piece was totally dry when I began to second turn it. I had soaked it in a DNA bath probably 4 or 5 months ago. It was left wrapped in newspaper (probably an additional 2 weeks) until it no longer lost weight, at which time the newspaper covering was removed. As a result it has been sitting on a counter in my shop for a few months at least - chances are slim that it was not totally dry.

Just wanted to see if these were due to poor (sanding) technique. I power sand at slow speeds but didn't know if this problem was operator induced. Glad to confirm that it was probably not due to anything I did.