I am turning a red oak bowl and have several cracks that have developed.
>What is the best way to repair this?
You can use the two part epoxies available at most hardware stores and home centers. You can color these with artist's acrylic (it does not take much) or you can add powdered stone ( eg turquoise, malachite, lapis) or brass (swarf from key grinding, usually free from people who grind keys). As an alternate, pack the crack with the stone or whateve and drip on thin CA glue. CA stains some woods,(I don't know about red oak), test on scrap and if it stains, seal the area around the crack with Deft or a similar product befor you inlay the crack
Bluntly, there is no unsightly way to repair a cracked bowl. Cracked bowls are look at on a case by case basis. Epoxy does not adhere well on oily and porous wood. Traditionally, acetone is used to remove oxidation and natural oil before using epoxy. Even at that teak and oak need mechanical devices (screws, dowels and joinery) to provide a good bonding. Depending on the structural nature of the cracks many woodturners do take advantage of these hairline openings. Providing that the structure of the bowl is sound, the cracks are filled with CA clue to enhance the beauty of the bowl. Filling agents are sometime used with colors according to the taste of the woodturner. The other day I was working at finishing a cracked bowl when a piece of red oak went airborne and struck my face shield. Since then many of the cracked bowls go directly into the woodstove. When making the rough blanks I try to make sure that the pit is completely removed and no apparent cracks are present before coating with Anchorseal.
"Am turning" seems to suggest over a period of time. As the cracks are certainly the result of green wood drying, your best advice is to schedule your turning to get the center out immediately after turning the outside. Failing that, bag your bowl in plastic when not working - I'll let Leif offer his alternative - to hold moisture.
Now, are the "cracks" just end checks caused by surface dryness, or are they the biggies that run through where the wall will be? If the former, turn them away and dry with care. If the latter, lots of advice, but red oak is not precious enough, in my opinion, to go to such lengths as others have mentioned. If it's otherwise ordinary wood, pitch and begin anew. If highly figured, have at it with either CA or Epoxy-supported fill, remembering that highly contrasting is usually preferable to similar.
Where do you find the crushed stone that you have mentioned? I have tried all of the rock and gem shops that are in the local Dallas/Ft. Worth area and even did a couple of searches on the Internet for "crushed gem stones", but no luck.
Actually I have chips of turquoise that I powder up myself (turquoise and malachite are soft enough to hand crush), but I believe that Craft Supply used to sell powdered stone. Don't remember the chip supplier, it was someplace I stumbled on when visiting New Mexico. You might also try jewelry maker's supply firms like Rio Grand (in Albuquerque) or Fire Mountain (somewhere in OR)
I haven't as yet ever used stain on turnings so I can't comment, but I haven't had probems with oil varnish mixes adhereing to areas that I've hit with CA, either in cases where I sealed before application or not (the latter for woods that the CA did not discolor.) May I ask what finish(es) you have observed this with??
Removing the pit as quickly as possible may work with oak more so right after the tree has been cut. With fruit wood, ash and at time oak my mentor suggested to fill the inside of the rough bowl with wet wood chips and then place the bowl into a plastic bag. When in doubt it was suggested to apply three coats of Anchorseal. The other thing suggested was that when roughing the bowl the wall thickness should be about 10% of diameter of the rough bowl. The wall thickness should be uniform throughout so as not to create stress points. I have noticed that the wall thickness of most of my cracked oak and ash bowls are not uniformed and consistent. FWIW
Even worse than the staining of the wood, CA is so thin that it wicks a lot further into the wood than the crack, and effectively seals the wood and prevents it from taking finish, stain or anything else.
As for locating the "powdered stone", you pretty much have to powder it yourself, which there is another thread about, somewhere on here.
-- Chuck *#:^) chaz3913(AT)yahoo(DOT)com Anti-spam sig: please remove "NO SPAM" from e-mail address to reply. <
Hmmmmmm I think you should tell the Gugeon brothers about this because they might find all of their beautiful yachts are falling apart. I suggest you get a copy of their information pamphlet from Lee Valley Tools and read up on West System Epoxy
This is kind of interesting. On water pased poly, one can say, OK, solvent polarity differences. But "danish oil" (the commercial varieties) is probably a mix of varnish and tung or linseed oil - chemically similar to what I concoct at home and use pretty much w/o problems. Ditto for "cellulose sanding sealer" which I am guessing is lacquer based.
I own a sailboat and build numerous dinghies and repaired several small boats using epoxy and different type of wood. In boat building when working with oak and teak, biscuits, screws, dowels and joinery are using with epoxy to obtain a good bonding
When I had delaminating problems in boat building I contacted the Tech. Department at Gougeon Brothers, Inc Should you need more information I can email you what I received from Tom Pawlak Technical Service at Gougeon Brothers, Inc or you can contact them directly.
Gougeon Brothers, Inc.
100 Patterson Ave., PO Box 908 Bay City, MI 48707-0908 U.S.A. tel: 989-684-7286 fax: 989-684-1287 URL:
Our variety of red oak, the genuine Q. rubrum, behaves superbly when drying. The measures you suggest have proven unnecessary, even for year-old logs. Truth be known, I haven't ever used any of them more than a few times, because I discovered benign neglect was all that I needed. That I am more than willing to give! I have a basement. If the NB is New Brunswick, you should have the same available, I would think. White oak, with its larger ray figure might be different. Don't know, as it doesn't grow this far north.
The bottom thickness business is mentioned often, but on a bowl cut across the grain, that 's the part under the least radial stress, which is generated by the early wood shrinking. It's also normally tapered to what will become the bottom, reducing actual cross-grain section to a minimum. Wood technology says there should not be a problem. My experience is the same.
Are the people who have trouble leaving the bottoms of their bowls thick also leaving them exceptionally wide, rather than tapering inside and out? The only bowls that consistently cracked for me were the ones with vertical sides. That makes sense, since the stress developed by shrinkage between the close rings cannot be relieved obliquely. When I used to fuss over drying methods the first deformation I observed was a "fold" at the ends, which would have been the result of the bottom shrinking across the grain. This appeared prior to the upward bulge - what our brothers of the flat call "crown"- generated by shrinkage between tightly curved annual rings dropping the long grain edges. The key evidence that stress is relieved by shape shows when the crown on the inside of the bowl - the part with most wood underneath, rises more than the outside, a mere inch away.
Oh yes, I haven't yet figured out why someone would coat the interior of a bowl with a sealer, as the natural drying geometry will close those pores, even as it tries to spread the outside. One thing for sure - hold moisture in too long and you get mildew.
Yes, NB stands for New Brunswick. One more things I was reprimanded by one of my mentor is not to store my blanks for drying with the bottoms up but with bottom down instead. That is without anchorseal on the inside.
Not a bad idea. Today I felled a birch tree and bucked 20 blanks. They have been trimmed on the band saw and ready to be rough out on the lathe. I'll experiment with standing them on edge ( like a book) with a slight angle for drying. This way I might be saving space during the drying period.
I have use CA to seal a crack and the used teak oil. It left an uncolored area where the CA wicked into the wood. It dosen't show up when you use poly or a wax, like briwax, as the finish.
InspirePoint website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.