Aging yellow cedar

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Attaining the look of naturally aged yellow cedar. September 2, 2002

I have just taken an order for 5,000 board feet of clear, vertical grain, old growth Alaska yellow cedar, 2" x 10" siding. The logs are in inventory and cutting will start on Monday. My customer has asked me a question that stumped me.

He wants to let the AYC weather naturally to a silver-gray color. I know from experience that up here (Pacific Northwest), the combination of rain and UV does the trick in a couple of years, but I don't know how it will behave in Southern California (Santa Cruz). The wood will be kiln dried (after a couple of months of air drying), surfaced and installed. The customer does not want any coatings, stains, etc. on the surface.

Is there any chemical "accelerator" that will hasten the weathering? The other concern is that the siding will weather differently on different parts of the house. (It has 6' overhangs on the east and west side, none on the north or south side.) The customer desires an even (non-mottled) look. This is extremely expensive siding and I want to do it right from the beginning.

Forum Responses
The siding will weather to different colors on different sides and under the overhang, as UV and water both accelerate the reaction. The best choice is to use a gray-silver penetrating stain as the wood weathers. You will notice that the yellow color turns to gray rapidly in sun and water exposures, but can you wait a year or more? This color difference is not like the color we see in walnut, beech, cherry, etc., as these woods are kept dry and inside a house.

Gene Wengert, forum technical advisor

From the original questioner:
As it happens, the customer is prepared to wait as long as necessary to achieve the desired results. On a visit to our mill, he saw some large flitches that had been sitting in the weather for 16 months. The color was so appealing to him that it made any artificial stains pale by comparison. I have to agree that the natural surface degradation takes on a quality and patina that I have never seen duplicated artificially.

One avenue we have explored is leaving the wood outside here, watering daily during the summer, and monitoring the progress. Hopefully, we will eventually get to the desired effect.

I agree that a penetrating sealer / preservative is in order, however, I cannot find any without UV blockers. Are you aware of such a sealer?

Once we achieve the desired color affect (silver / gray), can we stabilize it? (Surface waterproofing comes to mind?)

Oven cleaner will give a graying effect on some woods. You could try that.

You might want to touch base with The Heartwood Corporation. They manufacture Timber=Tek UV finishes. They also have preservative materials. One of the finishes, I believe, is just what you are looking for. It is a gorgeous gray tint color. They are located in Portland, Oregon.

From contributor A:
In the past, what we call "scrub" tabletops were quite common in the UK. Basically, they would scrub a sycamore or maple tabletop till it was bone white. Generally they would use bleach of some type. I don't know what you would use in the USA, but I've tried the bleach they use to clean milking machine pipelines (hydrochlorite?). It seems to do the trick. It's better to experiment with different concentrations, and remember to wash off, as if left on too long in too concentrated form, it does soften the wood.

From contributor N:
Dairymen here use sodium hypochlorite. It's just household bleach. EPA requires such products used for producing food to be registered with them so they buy an "EPA number", put it on a fancy label with a catchy name and sell it for three or four times the money, but it is just common household bleach. It's used to sanitize rather than clean the dairy equipment.

Sodium hypochlorite is the ingredient in both dairy equipment sanitizers and household bleaches, with the sanitizers being sold with a higher concentration than ordinary bleaches. However, I don't know if sodium hypochlorite will work for this application because it is unstable in sunlight and rapidly decomposes to a little chlorine gas and water. If you notice, both products are sold in opaque plastic bottles so they are not exposed to light.

From contributor A:
Perhaps it is possible to spray this bleach on the exposed surface just to accelerate the weathering, but always dilute as it can be pretty strong stuff, and hose the boards to further dilute the mixture and wash off once the colour required is reached.

From contributor N:
It is common in our area to use a bleach solution and high pressure washers to renew decks and natural wood siding. It removes mildew and often makes the wood look almost new. If I understand, that's the opposite of what the contributor is looking for.

We have some southern yellow pine siding that has never been treated with anything. It has aged to an attractive silver -grey color with some yellow and gold where there are knots and pitch streaks. You don't have 50 years to see what yours will look like in time, but you could look for some old buildings to see how they look now if left untreated.

Potasium permangenate is another aging accelerator. It is a strong oxidizer. I have used it to match flooring repairs. I don't know just how it would work outside. It is available at plumbing supply houses. Don't let the bright purple color fool you. It goes away fast. Use the customary precautions when handling the dry powder or crystals. Just mix into water until no more will dissolve.

From contributor N:
Just reread your original question and had a thought that might be of help to you. It's easy to get tied up in your customer's projects and sawing something for an unusual use helps make life interesting, *but* sometimes it is more prudent to just find out what he wants cut, what size, how much, etc. Do the best job you can cutting it, and let him worry (and be responsible) about how he goes about using it.

We sell almost entirely to brokers now, but I remember trying to talk customers out of using lumber I sold them to do things I'm sure wouldn't work well. Didn't feel good about it.

I have to agree. Cut good wood for the sap, give good advice and move forward. Tell the customer all you know about stains and UV and rain and such but make it clear that you are the expert when it comes to milling the lumber. There are plenty of painters in S. Cal that can give him the Bob V. patina he is looking for. Plead ignorant on that front, but let him know he will never get better siding anywhere else. You are the expert!

Woodworkers will sometimes use a weak muriatic/hydrochloric acid solution to age cherry. Spray it on to give it a little sunburn like UV and wash it off good.

The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).

Comment from contributor B:
Here at Forintek, over the last 30 years, we have noticed (through customer complaints) that yellow cedar tends to weather much more quickly than other softwoods. Therefore, exposing the wood to sunshine is an excellent way to develop the natural grey color. Of course, in spite of the natural oils and extractives in yc, the lignin-bond seems to break down more rapidly, and the brown lignin gets washed away with rainwater, leaving the cellulosic white wood fibers on the surface. One can actually rob off the loose fibers by wetting the weathered surface. For the above reasons I had a clear yellow-cedar Transylvanian gate pressure treated with CCA.

Comment from contributor R:
Cabot's Bleaching Oil has been around for over 100 years and does a nice job of aging any untreated wood. It works especially well (and probably best) on cedar siding. Google it and you will find hundreds of testimonials. It uses a mild bleach with a slight (very slight) bit of gray tinting. You check the exterior of the house every 3-5 years to see when it needs reapplication. I have used it on T1-11 cedar channel siding as well as western red cedar shingles. It does a good job of weathering the wood in about 4-8 months and looks very natural. It is, however, a finish that you will need to continue to apply through the life of the wood, but is luckily very easy to apply.

This may or may not be what you are looking for, and I agree with a previous poster that you need to educate the user about the wood and the various coatings and then let him do his thing. I would not try to age it yourself unless you want to offer to precoat it with Cabot's.