So, here's a confession: These clouds were a wedding present for a family member who'd liked the ones I carved on my 'Lark Ascending' Music Stand. The stand was carved in Sycamore, a white wood. I chose Oak for this carving because it echoed the originals in Kyoto which were a lovely, deep brown colour. I was well into the carving when I grasped that it was the whiteness of my previous clouds, as well as their shapes, that was so appealing to the recipient...
Always up for a challenge I finished the carving, set about making the clouds white and, in the end, the colour and effect were successful. And the carvings were very happily received!
But the whole was an experiment and I did experiment on offcuts from the original block first.
Bleaching a dark wood will never give the big whiteness you get by starting with a white or much paler wood. that And liming wax only works with open-grained wood like Oak. If I was to carve these clouds again, I'd choose a light coloured wood to start with, as I did with my music stand.
Bleach: I use a 2-part wood bleach, made by Rustin's (UK). Follow the instructions and be careful not to get the liquid on your skin. Use latex gloves for protection.