Repairing Split Wood

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In an otherwise attractive piece of wood, an unsightly split or crack can run deep like family turmoil.  Most wood fillers are intended to be little more than aesthetic solutions.  Even the hardiest fillers are intended to withstand compressive forces but not sheer stress.  Here I will demonstrate my solution for when I don't want to give-up on a piece of wood.  This block was salvaged from a eucalyptus tree that fell on my grandmother's house (don't worry, I'm fine).  I want to be able to work on it without risk of further splittage.  
  I do all my wood repair at TechShop.

Step 1: Supplies

I have found polyester resin to the be ideal for this kind of repair.  It is very strong in it's cured state, it seeps into fibers and produces a strong bond (it's intended use is laminating wood and resining fiberglass) and it is slightly flexible, so it will move with wood as it bends and expands with humidity.  

  *Not pictured: the necessary plastic bag

Step 2: Prep

I prefer jet black for most wood replair work.  I have given-up trying to match wood colors when disguising a crack.  In dark wood a black fill won't stand-out much, and in light wood it can look like the figuring of white ebony or cappuccino gelato.  It's my piece, don't judge me.  Specialized pigments are available for resin, though I have found almost any black coloring works.  Here I am using black airbrush paint.  A little bit of it goes a long way.
  Tape-up the sides and bottom of the piece to keep the resin inside.  Cracks run deep, so it is sometimes wise to tape the entire piece inside a plastic bag.  Do the repair work before making any cuts or planing on the wood and don't worry about the resin puddling on the outside.  

Step 3: Pour

Pour it in the cracks until it overflows.  

Step 4: And Use the Bag

Just to keep everything within the confines of the wood, I taped a bag around it. 

Step 5: The Unveiling

You got resin everywhere.  It's a good thing we used the plastic bag.  

Step 6: Finished

Polyester resin can be worked with most woodworking tools.  Be careful if you choose to go at it with a chisel, the excess resin will throw-off glass-like shards when impacted.  A bandsaw will cut easily and safely, then the resin can be planed, routed, or sanded.  This is a structural repair, so the block is now fit for any purpose as a solid piece.

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    203 Discussions

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    gfc62

    a few seconds ago

    Did you approve use of this instructable by Ted’s Woodworking? I received an email from him that appears to be copied from your instructable. I thought you should know in case your content was stolen. I’m happy to forward the email if you’d like to see it.

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    kieshar

    Question 7 weeks ago

    Is there a brand of Epoxy do you prefer to use for your instructable?

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    timsmith90

    1 year ago

    I don't think the resin would increase the structural strength of the timber. Clamping the timber with a wood glue is a better solution as it will be stronger and not split the same way again. The resin is just a filler not a form of strengthening which was required in your above posting.

    1 reply
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    Spence1953timsmith90

    Reply 5 months ago

    I'd be very surprised if splits in lumber, as shown by Scotttland, could be closed up by clamping. Wood glue is not a filler...so if one cannot get excellent contact between surfaces, then wood glue is NOT called for. Epoxy is typically called upon for filling gaps and adding strength. I agree that polyester resin is a filler that is not likely to be a form of strengthening, however, I don't know where you saw the requirement for strengthening in the wood used in this Instructable. I took it for granted Scotttland was going to carve it or otherwise use it artistically.

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    DianaA76

    Question 8 months ago on Step 1

    Hi there, may I ask what exact resin you have used. If I'm correct, usually resin is drying in a red or pink-ish colour to show when it's perfect. As I'm looking to poor it into wood (as yourself) I do prefer a neutral or transparent colour so I can mix it with dark and it doesn't have a pink or red tinch. Thanks for your help.

    1 more answer
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    Spence1953DianaA76

    Answer 5 months ago

    I am not familiar with the red or pinkish tint of set resin that you speak of. Perhaps that is a "feature" of a certain brand. To my knowledge, the typical set resin is clear or nearly clear. I would expect that whatever brand you consider buying, the color of the set resin will be disclosed somewhere in the description or the technical specifications.

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    AliH278

    Question 7 months ago on Introduction

    What do you recommend for wood that's splitting like in these pictures? I'm trying to restore this wood ladder, but the wood is splitting and in some places is splitting all the way through. It might be a lost cause, but I'd love to give it a try with a little direction! Thanks!

    IMG_20180317_152412.jpgIMG_20180317_152415.jpgIMG_20180317_152442.jpg
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    Spence1953AliH278

    Answer 5 months ago

    If you intend to "restore this wood ladder" in order to continue using this as a ladder, then I'd say there is no way to repair the wood to reliably restore the strength required to say the ladder is safe. If you merely want to use the ladder as a decoration or part of an artistic composition, then the resin used above or an epoxy could be employed.

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    DavidF559

    1 year ago

    Hi Folks.
    I'm hoping somebody can advise me on the best approach for a project I wish to complete this summer. After reading through the comments I have discovered some answers to several questions but I'm still not sure of the best approach.

    The project is a large outdoor table. It will be bar height and constructed of a large beech stump acting as the table base and the top will be a very large ring of beech roughly 10 inches thick. I need some advise as how to treat it to stop splitting and how to finish.
    I had the idea to coat the top after flattening with a router jig with an outdoor epoxy to achieve a glass like finish and possibly fill the surface cracks with a glow powder/epoxy mix. Will this work? Should I soak with an oil first before applying the epoxy like in previous comments?
    As for the base I was thinking of sealing the bottom/root section after flattening with an epoxy to prevent rot and stop any moisture being soaked up through the base. As for the rest of the base I plan on carving with various tools to depict a historical science from Irish folklore.
    I know this sounds like a crazy project but I really think it would look amazing if I can pull it off.
    All advise and comments welcome
    Thanks in advance

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    Jimichan

    1 year ago

    You should try clear resin with a glow-in-the-dark powdered pigment. It's fairly inexpensive on Amazon.

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    Hayilabc

    2 years ago

    Will this work for surface "cracks"? We bought a table with a checkered wood detail but there are areas where the wood is missing. They are about 1/8 of an inch deep. Any advice on whether this process might work?

    image.jpegimage.jpeg
    3 replies
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    KellyCraigHayilabc

    Reply 2 years ago

    For those dealing with cracked beams and such, the ideal is to address the problem before it starts.

    Sealing the wood doesn't work. Eventually, the wood will still lose moisture, which causes it to shrink, resulting in splits and cracks. I purchased a maple cutting board with this problem, then restored it using the approach noted below.

    For the butcher block, I flooded the top with mineral oil. The first bottle disappeared almost as soon as I put it on. The second went in slower, so I just added more to the spots that soaked in each time I walked past to another project. Finally, it began taking the oil in rather slowly. At that point, I slathered on a generous layer and just walked way.

    I ignored the top for a couple weeks. When I checked on it again, the oil had all soaked in. Too, it swelled the wood, just as water would, causing ALL the cracks and separations to close.

    The same approach can be taken with exterior wood surfaces. If you applied a generous first application, the obviousness of your efforts would disappear shortly. A second application would fare only a bit better. However, the third or additional coats would remain evident for years.

    The oil applications do not evaporate. They disappear because the oil wicks to the next dry area, deeper in the wood, until there is too little oil to wick further or the saturation has equalized throughout the wood.

    The main things, when using oils to replace lost moisture are:

    1) Use a non-hardening oil. That could be something like Chevron Shingle Oil (about ten dollars a gallon, in quantity), cheap motor oil (your mileage may vary) or mineral oil.

    2) To increase penetration, I'd thin it about ten or fifteen percent. You can use paint thinner, naphtha, mineral spirits or turpentine. I'd opt for the cheapest, unless I was working on a specialty project.

    3) The more aggressive and patient you are in your applications, the better your results will be. You can keep adding oil without doing anything to the surface, whether a day after an application or years after. The applications will build on each other .

    HINT: Buy the cheapest mineral oil you can for food grade items. That would be around a buck or so a pint.

    NOTES: Cedar shingles that are saturated with oil, in addition to not shrinking and splitting or cracking, will remain more resilient. Normally, walking on them in the middle of the summer would cause them to break. However, if they were saturated with oil, the would remain more flexible and less prone to breakage.

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    crf2720KellyCraig

    Reply 1 year ago

    After I saturate the wood with mineral oil and it swells, is it possible for me to stain and seal on top of that? Relatively new to finishing wood/woodworking and wanted to try this method before messing with the epoxy and everything. I am re-purposing some old 2" thick pine boards that are about 5.5" wide sections that are joined together to form a big butcher block almost. Ive attached a couple pictures of what I did with the board the first time, and what I am making this go around. The boards that I have left have been exposed to the weather for a while and have started cracking even though they are reinforced with 1/2" all thread trough both ends.

    IMG_0689.JPGIMG_1118.JPGIMG_0635.JPG
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    KellyCraigcrf2720

    Reply 1 year ago

    Sorry for being so slow to get back to you.

    Keep in mind, stain is, for the most part, a surface coat. Of course, much of it can get into cracks, grooves and open cells below the surface.

    If the wood isn't oozing oil, it shouldn't be any problem staining it. As they say, do a small test sample. Let it set the appropriate amount of time to see if it hardens. If it does, you're good to go.

    Water based stains aside, stains are made with linseed oil, a hardening oil. If you apply them to wood after the fact, they will act to seal the wood, at least to some degree. That will help seal moisture out and reduce moisture loss, in addition to what the oil does.

    Anyway, I would slather oil on the top, sides and, if practical, the bottom. Let it soak in, and let it set for a few weeks before applying the stain. Monitor some small cracks or splits to see if they are starting to close. If they are, you might want to drag the process out.

    When you think you've done all you can, go to the stain. If you are ready to bag it and move on, you can wash the excess off with a good oil busting dish soap. Just let it dry for a day or two before moving ahead.

    Again, remember oil is a surface coat and not the most durable/wearing finish, to say the least.

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    KellyCraig

    2 years ago

    I buy my epoxy in the gallon and a half containers (2-1 mix) and use it for cracks. The two to one mix seems much thinner than the fifty-fifty mixes I use, so it soaks in well.For
    light woods, I don't color the mix. No one has yet to notice the clear
    fill on in large cracks on a few butternut and other light wood
    ornaments I've made

    Painters' putty works good for sealing the
    end of the cracks. The portion with the putty can be cut off with a
    miter or other means.

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    PaulE61

    2 years ago

    @jimofoz, I am testing the epoxy method on scraps of wood before I work on my "live wood" table top that has several holes (some going right through the slab) but I have been having problems with the epoxy leaking through the tape. First I tried clear cellophane packing tape. No good. Then I tried hot glueing a cardboard to the bottom. Epoxy still leaked out. I haven't tried gaffer (duct) tape yet. Is that what you are using? Do you have some tips?

    4 replies
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    artobotPaulE61

    Reply 2 years ago

    Looks like he's using gorilla tape, thick, durable, and holds strong. Little bit more $ than a roll of duct tape, but it's worth it.

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    ChrisFosterlingPaulE61

    Reply 2 years ago

    I'm a little late to the party but after you apply the gorilla tape, I've had great luck in applying a little heat in the form of an iron on a low setting over a piece of cloth to soften the adhesive. Especially on wood grains.

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    headstackPaulE61

    Reply 2 years ago

    If you are hot gluing a patch over the through holes and getting "weep" it most likely means the patch does not have a perfect seal against an undulating/striated surface.

    Using something with better sealing capabilities like Phenoseal should work.

    I learned to use it as a "dam" around the top edges of cracks, so you can overfill and fair the filler down to grade after curing.

    Squirt a healthy bead well outside the perimiter of the hole, slap your patch in place, plastic wrap and then a slice of Masonite works well, and jam that sucker tightly in place to create a liquid tight seal.

    you'll want to make sure the caulk stays out of the hole so as not to blob up into the repair.

    Have fun!