Black spots in new varnished oak doors

[abetot]

I have just used a water based varnish to seal and varnish some new internal oak doors in a new house. Some of the doors had 2 coats on the first day and are fine. Some others had their second coat of the varnish on day 2 and have a few small black spots under the varnish. A number of other doors received their second coat of varnish on day 3 (2 days after the initial coat) and are covered in black spots.
These spots are within the wood and will not rub out, even with 60 grit paper.

My local paint supplier is blaming presevatives in the wood??

Has any one out there experienced a similar reaction or can tell me what is the cause of it please?

 

[Zampa]

Im no wood expert...but doesnt dampness or moisture turn some oaf black it it comes into contact with it?

 

[tonygerm]

if you cant rub it out its quiet possible that it could have been a nail or some sort of metal in the timber when it was alive or a possible deseas in the wood

 

[abetot]

Many thanks Tonygerm & Zampa for your opinions. I guess it could be to do with dampness in the wood as the spots look like some sort of mildew. I doubt that it is from steel in the wood as the doors which are affected are simply peppered with the black spots.

It is most strange that the doors worst affected are the ones that were left the longest between coats

 

[JohnD]

There is a thing called "blue stain" which I believe is a fungus. Don't know if that, or anything similar, is found in oak.

I expect Oilman will be along soon, he works in Oak joinery and will probably know.

I think though that it is more usual to give Oak an oil finish than varnish or paint.

 

[oilman]

I expect Oilman will be along soon, he works in Oak joinery and will probably know.

No I don't. Just goes to show how people can get a wrong impression. Biff Vernon is the guy you need. I wonder if it could be bits left over from rubbing with steel wool though.

I think though that it is more usual to give Oak an oil finish than varnish or paint.

Definitely. Much less hassle.