Turning Archive 2007

Question about cracks appearing in work

GolfSteve in Calgary
>I'm really new to turning, so this is probably something well known and avoidable if you have a brain larger than a peanut, but I'll ask anyway.

First of all, thanks for your help with my grain orientation question:

I ended up laminating a blank in a spindle turning orientation. The wood is maple, was kiln dried when I bought it, and has been in my shop for at least two years. It's not particularly great wood and has a lot of discoloration.

For a first "real" project, other than some pens, I turned a goblet with my daughter's face profile on the stem (there's a guy on the Internet calling these "pirolette's", but that does not seem to be a recognized word). He sells them for $149, and more power to him...this has taken me about 12 hours so far. Basically a patternmaking exercise was a challenging choice for my first project. The bowl started out at 8" diameter, but after a particularly spectacular fragmentation when I was doing a final clean-up on the rim, I was lucky to be left with a 7" diameter bowl. Here's a shot of the goblet as of a couple of days ago:

After turning the stem, I started hearing some "cracking" noises. The base had developed some cracks - my theory being that differential expansion was occuring due to the exposure of the goblet bottom to the atmosphere on only one side. Here's a picture of the cracks:

My question is - how could I have avoided this? Should I have parted away most of the waste on the underside of the stem bottom to allow for equal air circulation on both sides? Was it just bad luck or bad wood? I was leaving the material on the underside to keep the assembly strong...I'd had enough catches that I didn't want to inadvertently break the goblet away as I was finishing it up.

Santa Claus doesn't have enough time to start over, so he's ploughing ahead cracks and all. I turned away most of the waste under the base and soaked the underside with cyanoacrylate. Last night I sprayed the vase a dark cherry colour (dyed quite dark to even out the poor grain appearance), and was having great luck until my final topcoat of shellac when I sprayed a bit heavy and got a run....back to the sandpaper.

Thanks for your advice about the cracking,

The lathe sure makes a mess:

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