Acidity of wood for scales

[str8six]

I came across some mention that wood releases some acidity over time. Seems like that is indeed the case:

Corrosion of metals associated with wood - Victoria and Albert Museum

Wood and metal are usually regarded as highly compatible materials. However, interactions between certain metals and woods can take place under adverse conditions, or as a result of using unsuitable materials.

www.vam.ac.uk

This is concerning to me as my brother's woodworking hobby has been my go-to for scales and I like the linseed oil / beeswax finish he uses because it doesn't make the wood look and feel as plasticky as a shiny CA or urethane type coating. But maybe this is a bad idea and the oil/wax is insufficient to prevent acid from the wood from harming my blades over time?

I don't think it'll be a problem during my life as I store them carefully with VCI paper, don't let humidity build up, and I enjoy rotating through my collection so I'll catch it early if any corrosion develops.

I'm more concerned that I'm strapping nice blades to something mildly corrosive that will potentially hasten their demise if, after I'm gone, they wind up tossed in a box and stored without particular care for a few decades before being discovered again by someone who will appreciate them. Am I doing them a disservice with my choice of material? On the other hand, I've found some old blades with wood scales that seem to have survived quite some time without attention so probably it's a non-issue? Better than celluloid at any rate! Perhaps the porosity of the wood can help too in that it can absorb small increases in humidity from temperature changes?

Still, it seems this might be worth looking into and thinking about further. If nothing else, it's motivating me to take this into consideration when choosing the type of wood. Oak is apparently particularly acidic for example so now I'm going to investigate further in case I should hold off on some planned walnut scales...

Example of the linseed oil / beeswax finish:

 

[Ravenonrock]

Very nice craftsmanship on those scales, love the look of just the pivot pin. It would be a shame to have to replace those. As you say, just something to watch for at this point. I have some old wooden scales that have stood the test of time.

 

[Steve56]

I would suggest finishing wood scales with cyanoacrylate to seal the wood. You can also put a piece of Kapton tape on the inside of the scales to prevent metal-to-wood contact.

 

[StillShaving]

You could consider trying to resin impregnate the wood. Though I think that is somewhat involved, needing to dry out the wood and putting it under some pressure. I believe that is what Feather does to the wooden scales found on some Artist Club modles, making them more stablle and still feeling nice to the touch.

 

[Legion]

You could try magnolia wood. That’s been used for sword scabbards (saya) by the Japanese for centuries, and they wouldn’t use anything that might damage a priceless art sword.

 

[str8six]

Thanks, @Ravenonrock it'd be a shame indeed! Alas, not only is walnut on the acidic side, it seems like padauk (which these scales are made of) is one of the more acidic woods according to the table on pg. 15 of this:

https://www.researchgate.net/profile/Jean-Tetreault/publication/281295854_Coatings_for_Display_and_Storage_in_Museums/links/55e0c8dc08ae6abe6e8a02e4/Coatings-for-Display-and-Storage-in-Museums.pdf

Also need to look into the linseed oil, which seems to actually be used as a corrosion inhibitor ...but seemingly because of its carboxylic acid, which appears to be a more general term that includes the acetic acid the wood. Attempting to read about this stuff reminds me that I am not a chemist.

I appreciate the suggestion @Steve56 but I hope I don't have to resort to shiny CA as it detracts from the wood. And we do have so much plastic in the world it is kind of nice to have objects devoid of it, of course, we have so much because it is so very useful. The resin-stabilized wood @StillShaving mentions may have to be the compromise, but I'm still a bit in denial. I think ultimately I'm going to just have to be selective in the woods, oils and waxes I choose (appreciate the suggestion @Legion!) I do want to give these blades the best chance of surviving further centuries especially after, in some cases, having already made it through one or two.

Found another paper that reinforces my concerns, seems this is almost certainly going to have an effect: http://resource.npl.co.uk/docs/scie...ne_guides/pdf/corrosion_of_metals_by_wood.pdf

I also found that just reassuring enough to not tear the padauk off of my Mk10--temperature and humidity are what help release these compounds, and what enables them to corrode metal. At 72% humidity a 1% concentration of acid at 30C only causes trace corrosion. Unfortunately, I live somewhere where humidity hovers near 80% much of the time, not that hot though and my furnace/AC often reduces it. Explains why I've not really noticed anything as yet. Really must keep an eye on those though.

Seems like my current compromise of a cardboard box to retain the effects of VCI paper but allow humidity to equalise as the temperature changes may not be the best for these as "Acid vapours will not corrode if they blow away, but a small amount of ventilation is useless".

 

[Tomo]

I’m now a little concerned about the razor case I recently made out of an old humidor. The intent was to store the razors in a humidity controlled environment at 49% RH to prevent corrosion. The humidor however is lined in thick Cedar. I’m retrospect this may not have been a good move.

I must admit that I’ve started to notice faint ‘water spots’ on a few razors. Could this be the effect of the Cedar?

 

[Legion]

I’m now a little concerned about the razor case I recently made out of an old humidor. The intent was to store the razors in a humidity controlled environment at 49% RH to prevent corrosion. The humidor however is lined in thick Cedar. I’m retrospect this may not have been a good move.

I must admit that I’ve started to notice faint ‘water spots’ on a few razors. Could this be the effect of the Cedar?

Possibly. The nice smell that comes from cedar, and what keeps insects away, is caused by acidic gasses.

It’s probably good this thread made me dig out some text books, because I have a bunch of nice stuff stored in cedar boxes, and I might need to reassess that.

 

[Tomo]

Possibly. The nice smell that comes from cedar, and what keeps insects away, is caused by acidic gasses.

It’s probably good this thread made me dig out some text books, because I have a bunch of nice stuff stored in cedar boxes, and I might need to reassess that.

Good for cigars but possibly not so great for razors. Time to rethink things maybe.

 

[totorlekiller]

You could do the inside only with CA, that would avoid most of the potential problems without compromising the aesthetic of the wood.

 

[2bit_collie]

So don’t know much of anything about acidity of wood. But I notice that some related types of trees have species at the top and bottom of the list e.g. maple and poplar. That causes a 2nd thought to pop into my head. I have to think that the acidity of any plant is impacted by the acidity of the soil it grows in. So would expect that acidity varies sample to sample. This is reflected in some entries, not in others, which itself seems odd. Why would some tree species have a pH characterized to 0.1 while others vary over a range greater than 1.0?

 

[Jbird45]

As a woodworker, I applaud you for using a traditional finish. Boiled linseed oil, or BLO, and paste wax is a traditional finish and it is able to be maintained. Not all BLO is created equal though. The stuff from the big box store or hardware store has chemical agents in it to help it dry faster. Not exactly good for your skin. So wear gloves when applying. Natural BLO is just as it sounds, linseed oil, which is a type of flax seed I believe, that is boiled. It is actually a somewhat dangerous process, as I have heard the oil can catch fire somewhat easily. Also, as BLO dries, it releases heat, so don't leave a rag crumpled up on the bench. There is a small but real chance of it spontaneously combusting. No joke.

Now that I am done rambling, as far as your razors, I think humidity or cell-rot, if you have those kind of scales, are a much more credible threat than wood acidity. I have restored saws and hand planes that have sat in wooden tool boxes or barns for decades and brought them back to life. I have seen my share of tools that have seen the end of their life too, from neglect and careless owners, rotting away in a barn or shed. I also have tools from 150-200 years ago that are wonderful users. Its all about the care of the previous owner.

That being said, if and when the day comes to put your razors away for long term storage, my suggestion is to give it a good coat or oil and/or wax and rest easy. There's a channel on YouTube called Iraqveteran8888 I believe where he restores an antique Martini Henry rifle that was coated in ox fat or something and it was preserved for a century.

My whole point being, if you care for your razors now, and you put them away in a cared for condition, I don't see why anyone will have an issue decades later.

And certainly humidity is a much bigger threat than wood acidity.

This little Stanley No 4 I bought dirt cheap because it looked like it had been pulled out of a swamp. It cleaned up nice.

 

[str8six]

You could do the inside only with CA, that would avoid most of the potential problems

Probably not since a big concern is the vapor.

I have to think that the acidity of any plant is impacted by the acidity of the soil it grows in. So would expect that acidity varies sample to sample. This is reflected in some entries, not in others, which itself seems odd. Why would some tree species have a pH characterized to 0.1 while others vary over a range greater than 1.0?

Ha, you're probably quite right, would make sense there's a big impact just as terroir has quite an effect on various more delicious compounds. That could well be what's expressed by the range. It does seem that some species (eg. oak) are consistently highlighted as more acidic than others across a variety of sources however.

And certainly humidity is a much bigger threat than wood acidity.

...an old humidor. The intent was to store the razors in a humidity controlled environment at 49% RH to prevent corrosion.

Hm, well, if it succeeds at keeping them 49% RH and your location is typically a fair bit more humid than that the cedar might be helping more than not as that's below the level where rust starts to be much more likely. But if, say, your cedar box is in a room with an open window and cools off quickly allowing some moisture to condense. In that case, the acid would make it a better electrolyte and accelerate the rust.

Thanks @Jbird45, I appreciate the reassurance as I do intend to keep my existing scales (as I'm optimistic I'll manage to keep on top of any corrosion on my watch), and your point that oil or wax will help considerably in long term storage is a good one. But I can't discount what I've read entirely as I'm quite convinced museums wouldn't be going on at such lengths about it if it were a non-issue. Appears to be a pretty well established fact that wood potentiates corrosion and some wood more than others. It still takes humidity but the wood will make rust worse at the same levels.

Since we're rescaling the blades, it seems to me we may as well choose materials that give them the best chances in an uncertain future. Something might happen to me before I can properly put my collection in order. I might choose to sell one of my razors and it could end up in less careful hands, etc. I'm sure some will luck out and survive no matter what (especially the wedges as they're almost as tough as a plane iron) but if I make choices to give them better odds, perhaps a few more of them will.

 

[Jbird45]

Probably not since a big concern is the vapor.


Ha, you're probably quite right, would make sense there's a big impact just as terroir has quite an effect on various more delicious compounds. That could well be what's expressed by the range. It does seem that some species (eg. oak) are consistently highlighted as more acidic than others across a variety of sources however.



Hm, well, if it succeeds at keeping them 49% RH and your location is typically a fair bit more humid than that the cedar might be helping more than not as that's below the level where rust starts to be much more likely. But if, say, your cedar box is in a room with an open window and cools off quickly allowing some moisture to condense. In that case, the acid would make it a better electrolyte and accelerate the rust.

Thanks @Jbird45, I appreciate the reassurance as I do intend to keep my existing scales (as I'm optimistic I'll manage to keep on top of any corrosion on my watch), and your point that oil or wax will help considerably in long term storage is a good one. But I can't discount what I've read entirely as I'm quite convinced museums wouldn't be going on at such lengths about it if it were a non-issue. Appears to be a pretty well established fact that wood potentiates corrosion and some wood more than others. It still takes humidity but the wood will make rust worse at the same levels.

Since we're rescaling the blades, it seems to me we may as well choose materials that give them the best chances in an uncertain future. Something might happen to me before I can properly put my collection in order. I might choose to sell one of my razors and it could end up in less careful hands, etc. I'm sure some will luck out and survive no matter what (especially the wedges as they're almost as tough as a plane iron) but if I make choices to give them better odds, perhaps a few more of them will.

I have been thinking about this and I think I may have a possible solution to your problem.

The only part of the scales that is in contact with the iron would be the inside of the scales. If you were to coat the inside of the scales with some sort of film finish, say spar varnish or even a thin layer of epoxy, you would have a small barrier between the wood and metal, which would theoretically eliminate the chance of corrosion from wood acidity because it would no longer be in contact. And if you only did the inside of the scales, you can use the BLO wax finish on the outside, so it doesn't affect the feel.

You might be able to have your cake and eat it too