Linseed oil, old oak timbers and mould.

[RNReindeer]

I've made a mistake. I applied linseed oil to some old oak timbers, (internal timbers) and now I've got the dreaded (blue) mould.
I say 'dreaded', but I gather it's not dangerous, just unsightly.

I've googled the poblem fairly extensively and it's now obvious that linseed oil contains nourishment to feed and promote this mould, but only on oak. The mould spores being present in oak timber and allowed to grow when the nourishment is available.

So, how to rectify the problem.
If I apply danish, teak or tung oil will it sufficiently reduce the nourishment provided by linseed oil?
If I leave it, hoping that the nourishment will be exhausted, how long will I have to wait?
Or if I apply a varnish will it suffciently exclude oxygen to the mould preventing its growth?

Anyone experienced and rectified this problem before?

 

[AronSearle]

/Posting in a Rrrreeeender hamster thread.

Mould needs moisture, nutrients in oils are secondary to that.

It is unusual for oil to cause mould internally, as the amount of moisture added by finishes themselves is insignificant, it is more 'common' for this uncommon occurrence to happen externally with wetting.

Blue stain is not mould, it is not clear which you refer to but I suspect this. Blue stain is a fungus that occurs early in the timbers processing life and remains permanently in the timber, if it is blue stain it is likely already there and the oil just made it more visible.

Cleaning agents or bleach may reduce it's visibility, results may vary and experiment on a small area.

Also consider iron staining.

 

[RNReindeer]

Thanks for your interest, Aaron.
But the timbers are probably over 100 years old, have (AFAIAA) been internal all their life, so well dry.
There was no hint of mould or stain before. Apart fom woodworm treatments this appears to have been the first treatment that they have ever had.
It did turn the wood black, which I didn't mind, and after just a couple of days a patchy mould like substance appeared.

On the other newer timbers which is not oak, it's fine.

 

[AronSearle]

Have you looked up iron staining?

Did you clean with a wire wool brush, then apply moisture (which would be contained within the oil).

Pics would help.

The problem here is that you could have mould, blue stain, or iron stain, which can all look similar but have very different causes.

I suspect you have existing blue stain, which can just become more visible on application of a finish, or iron staining.

I would be very suprised to see mould caused by an internal application of oil.

 

[JohnD]

I have not used oak. But I have used linseed oil on exterior hard and softwood. It is not moisture proof and at first I got black stain. Subsequently I rubbed down and treated with Cuprinol clear before re-oiling and has been OK.

 

[RNReindeer]

I was aware of iron stain and I'm pretty sure it's not that, although I did use wire brushes during the clean up, extensively, as well as flap wheels.
The reason why I'm reasonably sure it's not iron staining is a) the fixings of the crook frames are wooden pegs and there are no metallic fixings, and b) the stain is definitely light blue'ish patches with bits of yellow and white. It rubs off easily.

The linseed oil was of course applied in a liquid form, but I wouldn't have thought there was suffcient moisture in it to cause mould and it didn't occur on the newer non-oak timbers, which did have metallic fixings.

Additionally another piece of similar timber has been extensively cleaned in the same manner but no oil of any sort applied and it's retained it's attractive dark oak colour without any sign of mould.

I can't supply a photo at the mo' 'cos I'm not there. (Xmas/New Year holidays)