Instructables
Picture of 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.
 
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Step 1: Supplies

Picture of 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

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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

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Pour it in the cracks until it overflows.  

Step 5: The Unveiling

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You got resin everywhere.  It's a good thing we used the plastic bag.  
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macnlaila1 month ago

would this work for 4x4 posts that are already cemented in the ground and splitting?

Looks beautiful! Kinda wish I had a piece of cracked wood sitting around that I could patch and make a unique project out of it. Awesome!

Huh. This gives me ideas for polymer clay sculptures. Now to find some suitably cracked, ugly heartwood knots. Thanks! :)

quinault4 months ago

I will use resin mixed with microballon, this will be the best putty

legamin6 months ago

gunna use this one! I've got all this gorgeous cherry wood and barn wood sitting about...

valveman2 years ago
I wonder if this would be a good idea for a cracked floor joist?
legamin valveman6 months ago

floor joists can be a. Replaced at high cost. Or b. Laminated with lam beam resins and 1/2" bolts 1 1/2" higher then lower (alternating) between two identical boards to the joist (to avoid turning or twisting). You should always go the entire length of the joist if possible or from load bearing wall to load bearing wall. If there is vertical compromise then at least several feet past the issue on both sides. Remember to do this while all load is removed from the joist. Rental of a couple twenty tonne jacks will do.

Wouldn't it be easier to just sandwich the cracked floor joist in between two non cracked replacements?
Not as strong. The non-cracked replacements only attach at a few points (between the screw heads & nuts, for instance.
Well, add glue to to the sandwich... Then it would become one...
So... pretty much what this Instructable does, only with bolts added.
No, he is filling a crack in this instructable... I was just saying you could face glue the boards and sandwich the two new uncracked supports. You wouldn't even have to use bolts... Just face glue and clamp... All depends on the severity of a cracked floor joist... If its structurally compromised, then simply filling it with an epoxy won't help much... However, if you are trying to fill it for cosmetic reasons then go for it... But I still wouldn't go this rout for a floor joist! I found this instructable very useful for wood turning pieces. In fact I think it adds a fantastic effect on the look of the piece...

What you are describing is called Sistering the Joists and I may be doing just that.
'Structurally' IMHO i think it would be a perfect idea for a cracked floor joist but then it really depends on how severely the cracked joist is and how much weight is being spread out on the joist but i work with these types of resin alot nowadays and love this instructable (MAJOR THANKS Scotttland !!!) but best to assess the cracked joist by a professional in the trade that makes/repairs these joists first, just to be safe !
Good info thanks.
Scotttland (author)  valveman2 years ago
I would second Mr. Offtherails point, and would recommend a replacement joist over even a mending plate or scab joint.
gsco00821 year ago
I was wondering... what if you use white wood glue and force it back in place with clamps until dry?
rlove41 year ago
great job Scotttland, I see you posted this a year ago but I've only just found it after a mention here http://www.instructables.com/id/Butt-Table/

you created much discussion and opinion as well, interesting thought that you should have just gone to the store if you wanted a piece of eucalyptus - not to mention just get yourself a seed and grow it lol.

I'm a time served vehicle body builder and we use a gelcoat inside fibreglass moulds to colour the job before laying up the matting and resin so it looks painted when it pops out.

it adds more depth to the colour to mix the gelcoat through the resin and if we were making something to take home or casting something we'd do that. there's a huge range of gel colours and they can be mixed together but they're expensive and we don't need much - I'd put a couple of BIG table-spoons in a pint of resin.

we worked with Ash quite a lot bus building so it would be used for the most humble of homejobs. most of the stock came in at just over a foot foot wide with the bottom end up to eighteen inches which gave quite a range to get what we needed (and as the company was paying no expense was spared) but sometimes we had to repair a piece doing just what you did.

most guys would mix glass fibre resin with clear gellcoat and sawdust from the bottom of the band saw. some just poured in brown gel and resin and some "celebrated" the split more than highlight it by using bright coloured gel, metal filings, tinsel, and even broken glass - some were succsessful and some couldn't be seen because even when used "clear" it's tea coloured at best.

if you want "invisible mending" whittle down a wedge to squeeze in the hole, when you've got a not bad fit take it out, half fill with resin and put the wedge back then use the whittlings to wedge in around it where you see resin then sand flat when gone off.- low tech marquetry but it works.

resin's really heavy on tools so always square and edge your wood first if you can (that goes for glue too). we had the cheapest of cheap electric plane just for hashy work to run over a couple of times to save sanding time but for a one off I'd not blunt mine.

used to vibrate with an orbital sander, paper masking tape is good enough, we put plasticine on endgrain splits unless it was quite big when we'd screw a thin piece of ply over the end grain.

acetone cleans resin off tools and lets you know without any doubt if you've got any cuts in your hands so wear gloves and take them off like a surgeon wrapping them inside each other. nail polish remover is acetone, expensive way to do it but good if you only want a small amount.
rlove4 rlove41 year ago
paragraph six should start "most guys would mix clear glass fibre resin without gellcoat to sawdust from the bandsaw
mbh21251 year ago
the wood looks great!
did you trim off a the top (most gnarly) layer of resin with a band saw to skim off the top layer or polyester resin, taking a small amount of wood off as well followed by plane/sanding?

the resin looks like tough stuff and would really dull down a hand plane -- plus you say it turns into glass like shards when hit with a chisel.
Scotttland (author)  mbh21251 year ago
I used a bandsaw then sanded. I don't recommend using a hand plane, however several tiny teeth each taking off small amounts of resin worked without issue.
What about the pull of a still-opening crack as the wood dries? Would that separate the filled crack?
Scotttland (author)  Woodyouliketo1 year ago
Once the wood is thoroughly dried, no further crackage should be an issue. This piece had been drying for a year before I repaired it. To prevent cracks in greener wood you can use Polyethylene Glycol, often marketed as PEG 1000 to evenly displace the moisture.
The filled crack will stay where it is, but if the wood continues to shrink, an additional crack can open up parallel to it.
temper2 years ago
Since the components are somewhat unusual it might be useful if you could indicate where abouts they may be sourced.
Any man store such as lowes home depot ace hardware true value.
Broom2 years ago
I would like to add one refinement to this method:
After you've taped off the ends to keep the resin from running out, clamp the split wood with C-clamps or a vice. Use backing boards if needed to avoid leaving marks. Your goal, if possible, is to force the splits closed, but if not, you should be able to squeeze them tighter together at least a little.

Then pour the resin on the break fault lines. Finally, remove the clamps. The vacuum created by the crack gap expanding back to its original shape will suck the glue in, deeper and faster than if you relied on gravity alone.

If necessary, add more resin after removing the clamps. The deep-penetration work has already been done, and the larger gaps that remain are easier to fill anyway.

In order to achieve the suction, the crack must be entirely covered on its entire length: either by tape (no gaps!), or resin. If there's a hole - say, if the crack goes through to the back side of the wood, but you haven't covered it with glue there - air will flow in much easier than resin.

It's OK to cover a two-sided crack on both sides. This isn't a delicate operation, and you can work quickly to try to get the clamps off before the resin on the bottom side drips off.
djokimaki2 years ago
Very well done Scottland! I will be using this one myself! I have some black walnut pieces that I've been wondering about. Maybe I will turn the wood vertical to fill it though, I think it may help to encase it in the plastic first, then let the resin work in from the end! Well done and thanks for sharing!!!
loopingz2 years ago
Interesting way to save some wood. It can be either decorative or not too bad structurally.
You might consider epoxy too (more expensive, easier to mix, stronger and less toxic). To use less resin you might consider to had some woodcell (or other microballoons). It will cost less in resin and be better mechanically. Anyway it will become less fluid so adjust to your needs.

Other than, for pooring resion consider wearing mask with ABEK1 filters. And you workout your result use P1 or P2 dust filters. I know two people that suffered huge pulmonary issue, really it is not a joke.
Melibokus2 years ago
That is fine. But should be seen different. As construction wood (outdoors) it is to "hard", if the peace gets wed, it shall "turn" and open again. Perhaps a hotmelt fits here better. Indoor wood do fit better. Because, polyesters as are used here, decrease on polymerization.
Manny B2 years ago
Just for the simple fact that you're a hilarious smart @ss, I'm going to subscribe to your posts. Go on!
chuckthehat2 years ago
I have a very nice solid body electric guitar that has a crack right through the area where the mounting lug is for the whammy bar. This is just what I need so that I can have my "strat" back! Thanks
Chuckthehat;
To fix the crack in mine, (also the stock on my 22 rifle), I used Gorilla Glue.
I used the light for the "stringer," and the dark on the rifle stock.
Worked great and have had no problems.
PS; That was way over 2 years ago
Okay im hooked !!!

Scotttland - This is a GREAT instructable !!!

Very nice pictures, nice and clear and i know hardwood is quite expensive around my area's and if i get hold of some discounted hardwood thats only cheaper because its got these types of cracks in it, Your PERFECTLY RIGHT - why discard it or destroy it when we can RE-PURPOSE and RE-CLAIM it to better suit our needs, not totally slamming the 'Go-Green' attitude as we will eventually run out of natural resources, but whilst they are still around, its better to recycle & re-purpose as much as we can nowadays !

Once again, a Darn-Great-Job on bringing this repair-idea into the light !

Even looks aesthetically pleasing to the eyes by using the Dye ! (so many colours, so many possibilities have now opened up !!!) NOW i want these cracked timbers just to make my finished work-pieces look artistic & unique !!! Really happy with this idea, made my day !

Just one question though, is the dye needing to be oil-based, to better mix with the resin ?

Sounds like it should be oil-based but just to make sure, what was the dye you used ?!?

Also many thanks in advance for the confirmation of the Dye you used !!!

Keep up the great work !!!
Scotttland (author)  offtherails20102 years ago
I've been using water-based airbrush paint and haven't had any problems.
sarawelder2 years ago
Fantastic! THe black will add greatly to pale wood. I wish I had used this to fill a hole in a spalted maple sculpture... next time. Very clear "ible"...I would like to know any other black dyes you have used and is it just a few drops? I imagine leather dye would work. well writen... but how is Grandma?
Scotttland (author)  sarawelder2 years ago
Grandma is good, no one was in the room when the tree came inside. I used a few drops of airbrush paint, that usually works well.
BobGarrish2 years ago
Very nice. I have a buddy who makes custom furniture using exactly this effect - he fills all the voids on really punky old barn beams etc with resin to make a smooth surface without removing the character from the pieces. The end result is beautiful!

http://www.rudefurnishings.com/
Scotttland (author)  BobGarrish2 years ago
Love this.
Nice looking stuff from that link. I was skeptical, but pictures don't lie.
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