What Happened to my Basswood / Limewood?

[Greg Davis]

I started a MS Bluenose kit a long time ago. After planking the hull I lost interest in the project and it has been sitting on a shelf out of the sun in a dry room where the temperature remains pretty constant all year long. When the hull was planked there was variation in the color of the basswood strips that had been supplied with the kit. About 25% were darker in color. Being new to the hobby, I used what was supplied and 'randomized' the use of strips. I have a picture of the hull taken in September of 2012 were the differing shades can be seen: 

I've been moving things around and happened upon the hull recently. Most all the strips have gotten a bit darker over time, but the darker strips (from early on) seem to have darkened dramatically more. 

Not being overly educated in wood, I am curious as to what is going on here. It is of particular interest as currently I am using holly for the first time on a model and the first holly I purchased had a good deal of bluish color mixed in. I now understand that the holly discoloration is likely a mold. Does basswood / limewood suffer similarly or is this completely unrelated.

 

In advance, thank you to anyone that can shed light on this phenomena.

 

Greg 

[vossiewulf]

It's just natural oxidation, although II don't know why the darker strips seem to be affected more. Anyway, all exposed wood changes color over time- cherry goes from pink to light brown and all woods darken. You can take a look at my build log and scroll back a bit to see a holly deck after five years, it only changes slightly to a cream color from bone white. I imagine it will continue to yellow over time.

[Snug Harbor Johnny]

  The amount of darkening varies from where in the tree a sample comes from  - heartwood (older and deeper in the tree trunk) verses 'sapwood' (more recent wood laid down towards the outside of a log as the tree grows).  There is likely a variation in chemistry.  Also, different trees of the same species can vary in color, possibly due to genetic variation as well as differences in the soli components/nutrition on the spot where each tree stands.

  I've had mahogany darken long after being completely sealed in a a French Polished shellac, so I can't see how oxygen could get through the coating. (Oxidation does change unprotected wood more rapidly.)  So perhaps the presence of light as well as a delayed chemical reaction may be the mechanism of action.  Yet the change is on or near the surface, so re-cut or freshly sanded wood is light in color.

[Greg Davis]

The oxidation idea sounds plausible. It is still a curiosity to me - there was no sunlight hitting the hull at anytime and the 'discolored' planks are discolored from front to back. Here is a picture of the inside of the hull:

There is little, if any, change in color of the pieces that had been taken from a laser cut sheet; i.e., bulkheads, stem, stern, keel. It seems to be isolated to the strips that were provided to plank the model. I've a number of MS kits and in many the planking material has a good deal of color variation (and at times quality and milling variation). I wonder if they don't always do a good job sourcing strip wood for their kits.  

[vossiewulf]

If you want more detailed info, I recommend R. Bruce Hoadley's Understanding Wood. I read it 30 years ago which means I've forgotten some of the details, but it is a really good explanation of the material we call wood and why it behaves the way it does.

[Gregory]

The wood for the strips and the laser cut parts could have come from different trees.  There may be different trees represented just among the strips, or at the least different parts of one tree.

 

The only reasonable assumptions you can make about the color variation with age, among  several pieces of wood, is when you know it was milled from the same stock.

[Gregory]

4 hours ago, vossiewulf said:

I recommend R. Bruce Hoadley's Understanding Wood.

Oh, wow!   I just learned more than I ever knew about wood just by reading the free sample on Amazon.

[Greg Davis]

21 minutes ago, Gregory said:

Oh, wow!   I just learned more than I ever knew about wood just by reading the free sample on Amazon.

the same is happening to me!

[Gregory]

I just bought a used copy on eBay for $10...   Long overdue addition to my library.

It looks like the new revised edition is a few dollars more, but the info about the revised edition says its about finishes an adhesives, and I am already fairly locked in on my preferences in that regard.

Edited Thursday at 01:25 AM by Gregory

[vossiewulf]

57 minutes ago, Gregory said:

Oh, wow!   I just learned more than I ever knew about wood just by reading the free sample on Amazon.

 

35 minutes ago, Greg Davis said:

the same is happening to me!

 

😊Glad I could help.