Hi Janey,
I'm not speaking from direct experience or specialist knowledge, but I think you've already come to the correct conclusion, tanning. I've found several websites listing a great many Victorian occupations & job titles, some of which are very odd and all interesting, but I've never seen the expression "bark dresser" in these sites; neither can my thorough searching find a single reference to this term.
I cannot see the Census image, but I doubt you've mis-read it.
The nearest "looking" occupation that I can find is a "bass (or bast) dresser", could that be it ?. Frankly that seems very unlikely from here, as this is someone in the fabric or mat making trade#.
However I think you're right and it's "bark dresser". Thanks to you I'm pleased to have learnt that tree bark is an essential part of the leather tanning process, the usual occupational name was barker or barkman. The term "dresser" appeared in many old job titles, someone who prepares the item (leather, flax, etc etc) for another process, using combs or other tools.
I suspect that in the typical apprenticeship way the young Evans lads at Broadoak were maybe given the less-skilled tasks in the joiner's workshop, in this case stripping the bark of newly felled wood and preparing it for the tanning process, perhaps then also cutting and storing the wood itself for seasoning, eventually ready for use by the more experienced and highly skiller joiner ? I thought I knew a little about the woodworking industry but I hadn't thought of this, guess it's only natural to find a practical and profitable use for the joiner's by-products.
I know Broadoak only in passing, I presume it's named thus as oak trees were/are prevalent in the area ? (I've tried researching but haven't found owt for sure). Apparently oak-bark is one of the best for the tanning process.
http://www.foresthistory.org/ASPNET/Publications/what_forests_give/sec5.htm
http://en.wikipedia.org/wiki/Tanbark
http://en.wikipedia.org/wiki/Bark_Mills
Thankyou once again for allowing me to learn something new and interesting !
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# This link is to the best definition I've found, from the Rootschat forum which seems the best place to ask such queries, as they have access to "The Dictionary of Occupational Terms", a book produced to enable census clerks to best interprete the census returns.
http://www.rootschat.com/forum/index.php?topic=388772.0
I've found several websites listing old occupations, such as:
http://www.familyresearcher.co.uk/glossary/Dictionary-of-Old-Occupations-Index.html#Old
http://rmhh.co.uk/occup/index.html
http://www.genproxy.co.uk/old_trades_occupations.htm
http://www.wakefieldfhs.org.uk/occupations.htm
http://www.census1891.com/occupations-b.htm