Replies

1. 
   Gretchen | Dec 03, 2003 12:41am | #1

   Carefully with a heat gun.

   Gretchen
1. 
   numbfinger | Dec 03, 2003 03:48am | #2

   Hmmm...I'm not sure that heat gun will get you your desired effect.

   The gray that you see on exterior wood is a combination of mold/mildew growth resulting from wet/dry cycles. My suggestion is to use an oil based finish, such as Zar or minwax, tinted to a light gray.

   After applying the finish, let it sit for a bit and use a rag soaked in mineral spirits to vigorously rub down the wood. This should give you a mottled gray appearance. We did a whole cabin in this fashion and the results were terrific... it made a brand new log home look as though it had been there for years.

   Keep in mind that the harder (denser) the wood,the more difficult it will be to get a mottled effect. You may want to try varying the pressure used to rub out the finish.

   Good luck!

1. 
   theshop1 | Dec 04, 2003 03:24am | #6

   Thanks to everyone who responded! I will give these all a try and see which would work the best.

   I'm not a slow carpenter nor a fast carpenter, I guess I must be a half-fast carpenter!

2. 
   Tao | Dec 03, 2003 05:51am | #3

   Lye (sodium hydroxide) isn't very safe, but it's fast. Make up a strong solution, pour or brush it on,  let it work, wash it off, neutralize with vinegar, rinse, and let dry.

   Lye is very caustic.  You need to wear gloves, eye protecton, and a rubber apron, and work very carefully so you don't get splashed.  You also need to have a safe place to work with plenty of water available, adequate drainage and where the lye won't damage things.  Outdoors is a good idea.  You'll have to experiment a little to get a routine that works on your wood in your conditions.

   Always add lye to water, not the other way around.

   A strong ammonia solution might do the same thing.  The graying is actually caused by degradation of the wood surface, primarily from ultraviolet light.  Wood stored out of the sun in barns and basements doesn't turn gray, even in damp locations.  Anything - acid or caustic - that causes similar degradation of the wood structure will give the same effect.

   It seems to me that I remember another, safer technique, but it's not coming to mind right now.  I'll follow up if it comes to me.

   If you want staining and glazing techniques, I have several.  Most involve blonding stains.

   Michael R

1. 
   numbfinger | Dec 03, 2003 11:42pm | #4

   Hi Mike...

   Perhaps you are right about the UV degradation. However, I was under the impression that the black streaks are actually growths of microscopic mold / mildew (thus we clean the wood by using controlled amounts of sodium hypochloride). I realize, of course, that UV plays an integral part in the destruction of wood fibers, but I am unsure why UV degradation would cause black or silver streaks.

   Perhaps you could explain the actual process that causes the gray / black appearance? Or in other words... what is happening to the wood fibers that cause the color change? I know that sap stain (or blue stain as it called in some parts of the country) is due to fungal activity, and I know that the truly black streaking is due to mold/mildew, but I guess I'm unsure as to why the wood would (snicker) turn gray? In my experience - wood left inside, next to windows with constant sun exposure, actually turns white,even if it started out relatively dark.

   I've been in the log home business for  awhile now, and I'd like to make sure that I'm explaining things correctly to my clients. Any input would be greatly appreciated. 

   Edited 12/3/2003 3:44:41 PM ET by petmonkey

1. 
   Tao | Dec 04, 2003 03:47am | #7

   PM,

   I was primarily talking about the silvery grey, since that was what the question was about.  You see lots of barn wood that is exposed to the elements for years, and just shows grey with little or no streaking.

   Bule stain is indeed caused by a fungus, but it grows while the wood is still green wet.  It doesn't grow below 19% moisure content in softwoods.

   Black streaks may very well be mold, as well as the black speckles you see sometimes.

   Wood can stay in a barn for 100 years without losing any appreciable color.  I have also seen wood that has come out of wet basements that is all black and gooey (mold), but doesn't show any grey when cleaned up.  That's why I conclude that UV is necessary for weathering.

   Lots of wood that is well drained and ventilated enough to never host mold turns sivery gray, I think from two reasons.  Ultraviolet light breaks down the lignin and other coloring agents, and exposure to rain leaches out the degraded materials.  Why silver / grey instead of tan or some other color?  I really don't know.  I'm speaking from observation and experience, not as a wood technologist.  I do know from experience that caustic materials can turn many woods grey without the assistance of mold or any other organism.  Just as I know that oxalic acid will partly reverse the process.

   I've seen quite a number of old log cabins, and from the look of the material, moisture caught in the cracks and checks in the wood, especially on shaded areas, probaly does support a lot of mold and mildew as well as the weathering I described, but the wood looks drty and drab, not the light silver grey of cleanly weathered wood -- like vertical grained barn siding.

   As for wood exposed to the sun indoors, glass is a pretty good UV blocker.  It doesn't get it all, but it's awfully hard to get a suntan through a window.  Enough gets throught to fade cloth, but the same cloth will seem to fade about 50 times faster outdoors -- again just my observation.  I've seen some upholstery fabrics lose most of their color in what seems like a couple of weeks outdoors.

   That's the basis for my opinions. If someone can elucidate further or correct me, I love to learn.

   Michael R

3. 
   Steinmetz | Dec 04, 2003 02:52am | #5

   Shop one, Move to Cape Cod, lay out the lumber on the 'Ruff'a cupla Yeahars, and Bingo!  Stein.

4. 
   Alan | Dec 04, 2003 03:50am | #8

   THESHOP1,

   If it's not too late for me to chime in...

   Cedar, and to a slightly lesser degree, redwood will turn a beautiful silvery gray with exposure to the sun and weather.  Cedar will darken and begin to silver rather rapidly; redwood more slowly.  Other woods may turn gray by themselves, but cedar and redwood are known for their beautiful silver color.

   I recently had to make a new gate for my mother's yard.  The fence and the old gate were made of cedar, and had begun to turn colors.  To get the gate to match the rest of the fence I used an outdoor stain that approximates the current color of the fence.  My thinking is that the wood will turn gray eventually, and until it does the stain will make it fit in with the rest of the fence.  With any luck the stain will be gone just as the gate turns the color of the rest of the fence.

   Alan

5. 
   jazzdogg | Dec 04, 2003 08:41pm | #9

   When I took a course in finishing, we applied mordant to several of our sample pieces. When applied to maple, it turned a very nice silvery gray in just minutes.

   The extent to which the mordant will darken the wood depends on the species' chemical content: oak darkens considerably more than maple because of oak's higher tanin content.

   The mordant we used was simple: a brew of vinegar and rusty metal. When used beneath dye or stain, mordants can significantly alter the wood's final appearance. By themselves, their effect is more subtle.

   Have fun experimenting on some scrap before you start finishing your completed project.

   Good luck,
   Paul

   Whether you think you can, or you think you can't, you're right.
1. 
   theshop1 | Dec 04, 2003 11:23pm | #10

   The wood that I'm using is cedar, and as Alan said in his post, cedar does turn a beautiful silver gray color. I did try a mixture of white vinagar and steel wool that I read about, and I didn't try it on cedar but I tried it on a wooden matchstick which turned  a light brownish color. I also tried a light gray stain that didn't give me the effect I wanted.  I will have to try some of the other suggestions and see if those will work. maybe I'm to fussy but I knows what I like :) This project is for myself on a room addition I added and it only took 24 years to get this far! To get the effect I want I may have to stick the wood outdoor for a  coupla years. Whats another two years, right?

1. 
   UncleDunc | Dec 05, 2003 01:46am | #11

   Have you thought of buying pre-weathered wood. I've seen barnwood in the building materials classifieds in my local newspaper. A google search for

   "barn wood" OR barnwood

   gives 33,000 hits, and I saw half a dozen sources on the first two pages. I saw one auction for barnwood lumber on eBay, but you'd have to take the whole barn. Lots and lots of things made of barnwood on eBay. You might contact some of the sellers about a source.

2. 
   ron61 | Dec 05, 2003 02:24am | #13

   I dought Iron Buff will work on cedar. It works great on Oak something with tanin  Im sure you can get a gray stain & maybe a glaze over it maybe .

    Go hear and ask Jeff he can for sure tell you what you need to know

   http://www.homesteadfinishing.com/index.htm

   Ron

2. 
   ron61 | Dec 05, 2003 02:15am | #12

   Iron Buff is what the brew of vinegar and rusty metal is called. It works I have use it- I just use new steel wool .

   The smell is gone after it drys. It will raise the grain also.

   Ron