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cracked bowl blank

H

herb

Joined
Mar 4, 2007
Messages
56
Likes
8
Location
Lakewood, Colorado
Hi,

Like many of you I turn larger bowl blanks from green wood. I've tried various ways of drying them. Currently I seal the end grain and stick them into paper bags - which is mostly successful. I turned a 16 inch blank of hybrid poplar and have noticed a crack in the rim. I have in the past filled voids and cracks with brass, but often it looks like "hm, a cracked bowl and crack filled with brass." Does anyone know of a way to rescue it is has it become fire wood?

Herb
 
I've had results similar to yours using brass and other metal fillers and I've never been happy with the finished product. But I've seen some work where a colored epoxy filler has been applied (after the wood has dried completely) that looked pretty good and the epoxy actually offered a bit of artistic character to a turned piece. Another idea that I've had (but never tried) is allowing the piece to dry completely, cutting it in half along a crack line (or just cutting out an area that includes the crack line and a bit of the surrounding wood material) and laminating in a filler piece of contrasting wood before remounting it on the lathe to finish turning it.
Then again, if you're not in the mood to experiment, I suppose it could always be used as fire starter as you mentioned😉.
 
A while back Jimmy or Johnny Tolly (sorry, I don't remember which) cut a cracked bowl in two and reassembled it with multiple brass rods and an inch or so of space between the two pieces. I though it looked amazing and cannot imagine how he managed to align the holes for the brass rods. He posted a picture on the Wood Magazine forum, I think.

Meanwhile have wondered if it would be feasible to steam a dried and cracked bowl and clamp it back together while it cooled and dried again. Then stabilize the crack lines with some CA. Might require a person with six hands and a box full of magic clamps. Has anyone tried this?
 
If it is a bowl that is intended to be used every day, I won't bother with fixing it. I just can't be sure that it will hold up to that kind of use. If it is an 'art' piece, I will fill and finish it.
robo hippy
 
"A crack at the rim" suggests one of the most common errors turners make when chainsawing blanks - failure to examine for preexisting cracks. The standard preparation answer of removing a good-sized center slab is no guarantee that you won't still include an existing heart check in your piece.

I find it helps to wet the blank and watch for wicking into unseen or poorly-seen heart checks. I will accept checks which run to ~4:00 or ~8:00 o'clock, because they will have little above to pull them open as the piece dries, and with the drop on the edges of a heart-up piece they will normally be turned away. If the checks are closer to vertical, I sometimes scoop them out with a gouge after turning, once again with the assumption that the rim will be turned down when dry. Stopping along an annual ring one beyond the last one visibly transected seems to work.

As to filling, you can try to make a virtue out of a necessity and use a contrasting fill, or you can whittle fill pieces from the same species which have the approximate annual interval and wedge each side to make a modestly visible repair. With some attention given to grain orientation and the annual match, they can be easily overlooked. Since branches originate at the center, you might even use the occasional cross-grain patch by using a branch and an appropriately-swept gouge to fit. Use a wedge on the other side, since both sides are not likely to be visible at once.
 
Epoxy mixed 1:1 by volume with fresh coffee grounds can make a handsome filler for large cracks. The dark part of the coffee grounds dissolves in the liquid epoxy, same as making coffee, and when sanded, lighter components of the coffee give an appearance of terrazzo.

But if done too often, it can become a "signature" feature, with the same ho-hum response that herb mentions.

I'd suggest limiting deep bowls to softer woods that can tolerate warping without cracking. For the others, a shallower profile is indicated. From a big log, three or four blanks can be cut from each cross section instead of two.

Joe
 
Cutting a very thin piece of endgrain from a blank will show cracks that otherwise are not visible. One can take additional cuts until solid wood is evident. I follow this procedure on wood where I have doubts. A smaller bowl without a cracked rim seems preferable.

Malcolm Smith.
 
Herb, sources for fill material are endless, if you turn any exotic woods save the shavings. I use brass as well but I also use dried flower petals, turquoise, malichite, lapis, etc. Depending on how big the crack is and how green the bowl I will often fill when green and after it opens up a little more I'll add another color of fill. Stops people in their tracks! The first time was out of neccessity now I regularly plan those types of fill. I use a dental pick to open the crack up just a little and you can pull the end out a little farther openning up whats there but unseen. Check out garage sales women will often get rid of their old gawdy jewelry for cheaper than you can buy bead chips for. I crush 'em up and keep two bottles a powder and a little grainier mixture for larger fills.

Good Luck,
Frank D.
 
Filler

In Utah I get "killer" cracks.

I have good success with wood shavings, dust and CA.
A trick is to first wipe an area around the crack with BLO to keep the CA from getting into the wood and leaving an ugly mark.

I sand and let the void fill with sawdust then use thin CA, building up layers.
I also put wood shavings in a coffee bean grinder to get it fine for the fill.

I recently used powder coat paint successfully, mixing it with 5min epoxy. I get the colors at http://www.eastwoodco.com/. BTW their powder coating system is stellar for painting acrylic pen barrels.

An example experiment is in the gallery (hope this link works) http://www.aawforum.org/photopost/showphoto.php?photo=5337&ppuser=1674.
 
Try carving

Try cutting the section out and do decorative carving around the bowl. If you can't hide it flaunt it. I had a vase that had a limb on the upper side. I cut it out plus some more and carved the edges. My wife called it the butt crack bowl. It sold right away and as fate would have it, it wound up as a flower vase in their bathroom.

Vernon
 
Cracks in Rim

How big is the crack?

I have several larger bowls that develop cracks during the drying. I try to inspect my stock of paper bagged rough outs periodically.

If I catch the crack small; I just superglue it! Sometimes - Maple or Pine, it will stop the crack.

If the crack is larger, more of a split - able to be filled; then I would think about filling it - or as Robo Hippy said - trash it unless it is an art piece.

John🙂
 
Malcolm Smith said:
Cutting a very thin piece of endgrain from a blank will show cracks that otherwise are not visible. One can take additional cuts until solid wood is evident. I follow this procedure on wood where I have doubts. A smaller bowl without a cracked rim seems preferable.

Malcolm Smith.
Click to expand...

You betcha. On rough-cut logs, you need to cut a slice anyway to square the ends. I saved a thin slab for part of a recent show'n'tell of a redbud bowl to illustrate its tendency to crack.

Joe
 
herb said:
Hi,

Like many of you I turn larger bowl blanks from green wood. I've tried various ways of drying them. Currently I seal the end grain and stick them into paper bags - which is mostly successful. I turned a 16 inch blank of hybrid poplar and have noticed a crack in the rim. I have in the past filled voids and cracks with brass, but often it looks like "hm, a cracked bowl and crack filled with brass." Does anyone know of a way to rescue it is has it become fire wood?

Herb
Click to expand...

Herb, The first thing to address is the removal of the pith of the blank. The area around the pith, out to about 2inches is a big source of trouble when drying blanks. Also, I have had very high success with boiling ruff-turned bowls. Put it in a big bucket, bring to a boil for one hour, shut off the heat, let it air out for an hour, then wrap the blank in several layers of newspaper and stick it in a bag for a couple weeks. You will find a very dry ruff- bowl when you open the bag. Then, remount it on the lathe and go for it! Phil
 
Since there is no mention of it, I'll add to this series that the effective way to avoid the cracks, at least most of the time, is twice turning. This also greatly reduces the drying time for blanks which other wise is years. The bowl, after the first turning, will become oval as one direction shrinks more than the other. This usually relieves the tension that is the cause of cracking. After it dries, one then re-turns the bowl so that it is round, not oval. The first turning needs to be thick enough that there is enough wood to allow the correction but not much more. There is a judgement involved that varies with different woods. After the first turning, it's not a bad idea to coat the wood to slow down the drying.

Malcolm Smith.
 
to turnedoutright

What is BLO?

A trick is to first wipe an area around the crack with BLO to keep the CA from getting into the wood and leaving an ugly mark.


squirrel
 
I finish the bowl with a kind of varnish. Then I take powder, whatever , white claypowder for example, and I put some powder in watercolour paint. Put this in the microwave - coloured powder will be left behind.
I mix this powder with the varnish and fill the crack. Take of what is left on the surface which is easy because it is already varnished. This kind of dying a neutral powder makes it possible to make your own colours, exactly as the colour of the wood is.

squirrel
 
Blo

Sorry for the acronym
BLO = Boiled Linseed Oil
I also use mineral oil.

I am fascinated by your method.
Let me see if i understand it:
  1. After finishing with varnish.
  2. You mix a neutral powder with water color paints to match the wood.
  3. Then you put it into the microwave to evaporate the water, leaving colored powder.
  4. Then you mix the colored powder with varnish and fill the cracks.
Questions:
What neutral powder do you use and from where?
How do you level the surface after filling the crack (doesn't it leave a bulge)?
Do you have a close up picture of the results?
Could you mix the neutral powder with wood dust and water then evaporate the water.

This is brilliant, gona try it 🙂
 
Turnedoutright said:
How do you level the surface after filling the crack (doesn't it leave a bulge)?
Click to expand...

If crack filling is deferred until after final turning, pretty much a lot of hand sanding (with a backing block to reduce ripples).

I've had better results by filling the cracks and voids before final turning. Even then, if the filler is substantially harder than the surrounding wood, expect some tool bounce, and sandpaper chatter too.

Joe
 
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