Repairing Split Wood

Intro: Repairing Split Wood

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.

Comments

[Boatdoc61]

We bought a 70 year old house that came with a really cool decorative 8 feet in diameter water wheel. It's wooden and still works, but there are several cracks within many of the wood pieces themselves as well as some gaps between the individual boards. I'm thinking that it will be look and work better if I can fill in the cracks and gaps and I'm also thinking that wood filler epoxy might be a good thing to use for that - but I thought I'd ask someone more expert than myself. Thanks for taking my question.

[rooniemag]

Hey, I've got a near microscopic split in a small project of mine (the project is under 5in x 1in x 0.5in and the split is thinner than my thumbnail). The split isn't invisible, but it runs through the whole piece and knowing me, I'm almost definitely going to pry it apart if left to my own devices. Will epoxy fit in a gap that small? If you're not sure, is there at least any way to dissolve epoxy so I can safely experiment? Many thanks.

(First image shows how far down it goes and has my index finger for reference, second image shows the path of the crack going deep. I'll be able to get better picutres once I have something that isn't my laptop's webcam, lol)

[niblick45]

I just turned a softball bat out of cedar and the wood was too green and the bat has a few splits in it, would this resin work do you think?

[hwallach]

What is the specific material you are using for this repair?

[jeff_berk1]

I think he is using TAP Bond Coat Laminating Polyester Resin but it's hard to know for sure from the photograph.
https://www.tapplastics.com/product/fiberglass/polyester_resins/tap_bond_coat_laminating_polyester_resin/37

[Mammoth_Media]

How long should the wood be kept wrapped?

[JOHNCONKLIN]

you do not state specifically what type of wood resin you use or where to buy it, i have retired in the hilipines and have an 3/16 crack through an 3 inch wood step please advise, john

[RickWW47]

Can you now use this on a wood lathe with safety?

[JasonB589]

Absolutely. I do it all the time.

[Hophead1]

Thanks for this.
Can the cured filler be turned on a wood lathe?

[JasonB589]

Absolutely. I do it all the time.

[Ncoonis1]

Thanks for a great article! Can you tell me what products you used or recommend for the project?

[MichaelW738]

I do the same thing on my canes only im using black epoxy. But, I give my personal 250 lbs. stress test. One arm handstand not included. I feel black works the best for all woods and adds character to the finished product. My favorite canes are made from brush piles and wood rot be damn. Just use a few coats of Miniwax's Wood Hardener. Of course I had to strategically paint an, "ie, "suffix on the end of one of the products 2 letter name.

My question to you is the brand and name of the resin you are using? It's got to be cheaper than the $6 tubes of epoxy I have.

Sincerely,

Mike Woodward
Lynchburg, VA

[gfc62]

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.

[kieshar]

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

[timsmith90]

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.

[Spence1953]

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.

[DianaA76]

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.

[Spence1953]

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.

[AliH278]

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!