"Stephen Howard" wrote in message
news
On Sun, 7 Aug 2005 18:23:08 +0100, "Trevor Appleton"
wrote:

Here we are in one of the driest parts of the country with only 16 inches
of
rain in the 50 weeks up to two weeks ago, and our new ( 2 month old) oak
table and chairs are black with mould.

Any suggestions how to :

a) Get rid of it

b) Keep it away

I'm wondering whether the problem might be down to a finish applied
to the Oak during manufacture of the furniture. Linseed oil is
typically used to treat such items, and it's about the worst finish
for wood that's exposed to the elements - the formation of a black
mould being pretty typical.

You can use a homemade wood cleaner/restorer, based on a recipe I use
in the workshop for professionally reconditioning wood, though if the
furniture has been varnished you might find you need to sandpaper it
first. Try it on an unobtrusive spot first and see how you get along.

4 parts groundnut ( or peanut ) oil
4 parts white malt vinegar
4 parts turps
1 parts methylated spirit

Nb: A Grolsch bottle makes an ideal container for this mixture!

A few drops of strong ammonia will help the 'cut' of the mix - but
household bleach will do. Feel free to add a few drops of essential
oils if you want to make the process a little more 'aromatic'
Bergamot oil is excellent, and Vetivert will impart a pleasant
'wood-smoke' scent to the mix.

Shake well, and apply as needed with plenty of elbow grease. For heavy
grime, use fine wire wool ( triple '0' gauge wool should be about
right for garden furniture ).
This mix works very well for indoor furniture too, though I would
recommend quadruple '0' gauge wire wool for application.

As regards prevention, you have two choices. An oil finish or a wax
finish.
Oil finishes seldom give satisfactory results on exterior wood (
unless you're scrupulous in the preparation of the surface...and who's
that scrupulous when it comes to garden furniture? ), and a drying oil
finish on Oak will cause it to darken over time...thus negating that
lovely 'silver' finish that Oak gives with age ( this is why mediaeval
oak furniture is nearly always black ).
Also, because of the relatively large pores in Oak you might find that
a drying oil finish - such as Tung oil etc. - leaves a 'bobbly'
surface, as oil leaches out of the pores and hardens in the sunlight.
Non drying oils give a better finish, but will need re-applying at
least annually - and this should be done in hot weather. Apply
sparingly and wipe of any excess for a couple of days afterwards.

Beeswax has long been known for its protective qualities, and a stiff
beeswax polish will work very well with Oak - though you might well
find that an annual clean with the above mixture will suffice.
You might find stiff beeswax polish hard to come by, in which case you
can knock it up yourself by dissolving beeswax in turps. Grating the
wax first will speed up the process. The mix ratio is down to trial
and error - try a few spoonfuls of grated wax to one spoonful of turps
and see how it goes. Add more turps as required to thin, or leave the
mix in the sun to thicken.
Apply the wax ( choose a hot day, when the wood is warm ) with fine
gauge wire wool to ensure it gets right into the grain, then cut the
excess off with clean wire wool before buffing to a finish with a
coarse cloth. It's pretty tough work - which is why most people slap
on a bottle of Tung or Danish oil and hope for the best.

Regards,



--
Stephen Howard - Woodwind repairs & period restorations
www.shwoodwind.co.uk
Emails to: showard{whoisat}shwoodwind{dot}co{dot}uk


Many thanks for the very detailed reply.