Cleaning off old Oak lintel

[chuckey]

I cleaned off a very old oak lintel, but the results were very disapointing. I have scraped old oak furniture and expect to get to a very light surface that changes to a honey colour with a bit of clear varnish. This lintel as presented was light coloured and dusty. As I planed it , scraped it, sanded it, it went to a chocolate colour - it looked as though the surface had been burnt by using a blocked sanding disc. The lintel had about 80% of it as heartwood (this was the bit that went dark) which was surrounded by a light coloured wood (worm eaten ) which stayed light. The wood had medullary rays so I think it was oak.
Does this mean that every piece of oak furniture I have worked on was non-heartwood? Can some one suggest what was going on here.
Frank

 

[middi]

The heartwood of old oak beams tend to assume a very " dark" patina especially if they have been reused at some stage in their life but left standing for a period of time in the elements before being reused. It appears that the tannic acid of the oak will cristallise ( as it normally does and goes very hard) but when left standing in the elements and reused it seems that when re-cut it assumes a darker "tone".

This is not a scientific explanation but one of observation. I cut an old beam once ( 8"x8") and the heartwood was a golden dark colour, left outside for about 12 years in the elements standing upright against some sheds amongst other wood . It was put under cover in a dry shed and recut a couple of years later. The colour was much, much darker.

As to why, I can only assume that the acidic rain and other air pollutants may have slowly bleached it and when re-dried it assumed a darker colour.

Middi