Filling cracks

Discussion in 'Woodturning Discussion Forum' started by olaf Vogel, Dec 4, 2016.

  1. olaf Vogel

    olaf Vogel

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    I'm trying to finish up a piece of heavily spalted maple, the wood is already dry.
    The plan is to finish it with shellac.
    But it has a few cracks that I would like to fill.

    Q1 - Is epoxy the best to use for filling? I have some high strength West Systems left over.
    Q2 - To keep the filled spot from spreading and causing staining when I finish, should I apply shellac first, then fill the cracks? or Fill first and finish second?

    IMG_1436.JPG IMG_1437.JPG
     
  2. Bill Boehme

    Bill Boehme Administrator Staff Member

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    First, given that the wood is dry, it should be fairly stable. In this particular case, the crack follows the growth ring and in my opinion isn't likely to change. A crack that is transverse to the growth rings would be of greater concern than this one. For aesthetic reasons it would be good to fill the defect if you are planning to have a glossy finish. You could use epoxy or CA, but first apply a wash coat of shellac to prevent local staining. I like to use Starbond Brown Medium CA (actually amber) for filling this type of defect because of its resinous appearance.
     
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  3. Raul McCai

    Raul McCai

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    Recently I got out a tool I built that I used a Locktite heavy duty epoxy from the BORG. I built the tool and put it away maybe last winter. When I tried to use it the epoxy was crumbling. Did I have a bad batch, a bad mixing job, bad luck? I don't know. But, that was definitely a bad experience with epoxy.
    Just putting it out there.
     
  4. Richard Coers

    Richard Coers

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    Have you used shellac on this kind of wood before? Just curious because I would just use a flat sheen artist fixatif to maintain that color. I usually use masking tape to tape off a crack like that, and fill with a fine sawdust/Titebond original mix. I mix it pretty dry, as much sawdust as it can hold.
     
  5. olaf Vogel

    olaf Vogel

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    Thats exactly what I was looking for. Thanks!
    I'll stick with epoxy for now as I've not had great luck with CA for this.
     
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  6. Mike Johnson

    Mike Johnson

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    You could try and match the color of the wood you are filling with the darker saw dust and wood glue.
    Or since you have spalting on the wood piece you could use a black pigment or black saw dust mixed
    with wood glue and fill the void and make it look like spalting.
    You can also add pigment to epoxy and accomplish the same affect.
    The wood glue solution is quick to test, mix up saw dust and wood glue and plug some drilled holes
    and let it dry and sand it smooth. This will allow you to figure out ahead of time how much and
    how dark of wood dust to add to get the desired affect.
     
  7. Owen Lowe

    Owen Lowe

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    Olaf,
    Epoxy is the way I’d go and in my experience it doesn’t really soak into the fibers and ruin the finish the way CA does. Soooo, I don’t think any pre-finish before the epoxy is necessary — however, it wouldn’t hurt any if you are wanting to put a barrier coating of shellac as epoxy sticks to just about anything.

    Raul,
    Crumbling epoxy sounds like mismatched resin and hardener. Poor mixing usually leads to a sticky, non-curing mess.
     
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  8. Mark Hepburn

    Mark Hepburn

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    Raul, I use the Loctite for lots of things and haven't had any failures to date. Was this a wood to wood bond, wood to metal or something else? I can tell you that sometimes it is finicky if you don't use equal portions so I weigh it with a little portion scale that I used to use in my bakery. Goes down to .1 gram but you can get one even more precise on Amazon for a few bucks.
     
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  9. odie

    odie

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    For those using either epoxy, or wood glue mixed with sanding dust.......Do you think it makes any difference to the final appearance, or adherence, how fine the dust is? At what stage of the sanding process, do you collect a specimen for this purpose? I think we can generally accept the premise that sanding dust collected from the bowl that will need a crack filled would be the best bet for ending up with a filled crack that best matches the wood.
     
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  10. MichaelMouse

    MichaelMouse

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    Whittle some wedges of wood, touch some medium CA cleanly into the gap, then slip the wedge(s) in until it fills. Don't wipe squeeze out, cut it later. If the grain orientation's different where the crack is found, make the wedge accordingly.

    My second choice is bark shavings, where bark is present in the piece, followed by crushed bark.

    The type of finish can give you the dead fish eye look if you use dust. Too much scatter.
     
  11. hockenbery

    hockenbery AAW Advisor Staff Member

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    Coffee grounds make a nice filler with epoxy or CA.

    Ed Brannon taught me this trick.
    When Ed Brannon asked to use some coffe grounds I thought he had lost his mind.
    The result of coffe grounds is a realistic looking defect in the wood. The texture and color of the grounds looks like a water stained rot spot.

    If you have the ability to make a crack disappear go for it. I always seen them.
    I gave up on hiding cracks - I now try to make them look like they were always there.
    Turn them into a natural looking defect
     
  12. Mike Johnson

    Mike Johnson

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    If the coffee grounds are not dark enough you can put them on a pan a slowly roast them
    in the oven until you get the color you need.
     
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  13. Ditto Hockenbery. Don't try to hide the crack/defect. No matter how hard you try, you can't match mother nature. I use dried coffee grounds and colored West System epoxy. - John
     
  14. odie

    odie

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    I'm not sure what I'll do with this black and white ebony bowl.....the darn thing cost me $97 after shipping. :(

    Mixed the epoxy with sanding dust, and I probably should have used more of the dust than I did. Can't really tell how it'll look until after it's dry and sanded flush......so, you get what you get!

    Here's the biggest crack.....it's about 3/32" wide. There were several other small cracks that were also filled.
    IMG_2459.JPG
    The bowl was finished this morning, except for the foot. This is with danish oil applied, no wax yet. I'm pleased that the crack appears somewhat camouflaged by the wood, but it still looks like a crack.
    IMG_2472.JPG
    IMG_2471.JPG
    Not sure what I'll do with this bowl at this point......... Sure would love to have some of this B&W Ebony that didn't split, but I heard this is a problem for this species. My sources usually only have spindle blocks on rare occasions.....mostly nothing good enough to make a bowl from.
     
    Last edited: Dec 12, 2016
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  15. Fred Belknap

    Fred Belknap

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    Beautiful bowl. I agree the epoxy should be a little darker but most people won't notice. I have patched some cracks with epoxy, I use Transtint Dye. It just takes a small amount to get a nice black finish. Usually a couple of drops on the end of a toothpick. I use the five minute epoxy and only mix a small amount at a time. I don't think you will have any problem selling the bowl.
     
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  16. Bill Boehme

    Bill Boehme Administrator Staff Member

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    Odie, I think that I would have used a Dremel tool and small diamond bit and filling with black epoxy to modify the crack by incorporating it into the wood color pattern as shown in the picture below:

    odiebowl2.JPG
     
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  17. Mike Johnson

    Mike Johnson

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    Odie,

    That is a nice looking bowl, if you did not know the crack was there you would need to look
    for it to notice it. I have seen some nicely done pieces where they used turquoise, silver, bronze
    or copper powder to fill in cracks and voids. With the black variations in the wood grain your
    solution looks as good as any other solution available. You could cradle the bowl in a three legged
    stand which would cover the crack on the outside of the bowl.
     
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  18. john lucas

    john lucas

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    Personally I don't like the sawdust crack repair on larger cracks. It looks like you filled it with pressed wood, not a good look. I do however use contrasting sawdust sometimes. I keep several jars with rich color wood sawdust such as ebony or redheart. I will use these. Still I prefer to use either the bark as or coffee grounds as suggested above. To me it makes a more natural look. I do like the look of colored epoxy and use that a lot. A crack running horizontally across the existing grain is impossible to hide so your much better off trying to make a feature out of it. Sometimes that needs using a dremel to reshape the crack so whatever filler you use will be come a highlight.
     
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  19. Mike Johnson

    Mike Johnson

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    The colored Milliput putty epoxy is quick and easy to use if the colors available will work.
     
  20. Joe Greiner

    Joe Greiner

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    Plus one for ground coffee and epoxy (I use 30-minute and fill proud of the final surface).

    Depending on brand and grind, the coffee has light and dark portions; when cut and sanded, it looks like miniature Terrazzo.
     
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