# Hairline crack in CA finish..grr!



## chriselle (Nov 5, 2008)

Ok, I've got the CA thing down pat but I don't know what to make of this.  I made this "kokutan" euro about three months ago and it has been sitting pretty in my shops showcase ever since.  I take it out the other day and to my horror it has a fracture.  I had a Padauk euro crack in a similar fashion about a year ago...4 months after I made it.  There are no heat issues in the showcase so the only thing I can think of is both pens were made in the summer months when the heat and humidity are umm..... brutal.  I always finish with 10 or so coats of Med CA so it may be a curing issue.  Have any of you had a similar problem?

Extreme closeup of the area.


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## leehljp (Nov 5, 2008)

Not across the grain like that. I have had two kokutan / kaki-persimmons crack lengthwise with small cracks, but refinishing fills in the cracks and they are OK.

Several suggestions for cracking - too much heat when drilling, too tight of a fit on the tubes. Snakewood is the worst, but with care some manage to drill and produce fine pens without cracks. It is my contention that some flexible glue and more space than just a tight fit - be allowed - so that brittle woods will be allowed to expand and contract more naturally.

Looking forward to others notes on this since it cracked across the grain.


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## chriselle (Nov 5, 2008)

Hank,  This is JUST in the CA!  The wood is fine.  It's a mystery to me.  I keep my CA fresh so that's ruled out, too.


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## rherrell (Nov 5, 2008)

My first thought is that 10 coats of med. CA is WAAAAAY too much. However, if all your pens have that many coats then maybe that's not it. I also use med. CA (no blo) and each coat is between .001" and .005", depending on how much sanding I do. I usually apply 2 to 3 coats and try to keep the total thickness to no more than .004"(.002" X 2). Any thicker than that and I have trouble with it lifting on the ends. Besides, 10 coats would take me an HOUR to apply!:wink::biggrin:


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## chriselle (Nov 5, 2008)

rherrell said:


> My first thought is that 10 coats of med. CA is WAAAAAY too much. However, if all your pens have that many coats then maybe that's not it. I also use med. CA (no blo) and each coat is between .001" and .005", depending on how much sanding I do. I usually apply 2 to 3 coats and try to keep the total thickness to no more than .004". Any thicker than that and I have trouble with the it lifting on the ends. Besides, 10 coats would take me an HOUR to apply!:wink::biggrin:



Yes, it is a lot Rick but I do a lot of sanding....I mean..A LOT.  Also, it takes several hours to apply.  I've never had any lifting and never a problem with building too thick.  I do think that I may have to re-evaluate the number of CA applications depending on season and relative humidity.


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## chriselle (Nov 5, 2008)

Sniffle...sniffle..  Here is the same pen just last week or so...:rain:


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## mrcook4570 (Nov 5, 2008)

What is the grain orientation of the wood?


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## chriselle (Nov 5, 2008)

mrcook4570 said:


> What is the grain orientation of the wood?



Stan, it is in fact crosscut.


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## leehljp (Nov 5, 2008)

chriselle said:


> Stan, it is in fact crosscut.



Was the wood stabilized by any chance before making it? If not, the expansion contraction with humidity changes 'can' definitely do that on many woods without the wood itself cracking.


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## MobilMan (Nov 5, 2008)

My thoughts also.  There may be the answer.  CA is also very brittle.  Also CA is a fairly new idea in finishing & things like this are bound to pop up at times.  Even tho the naked eye may not detect the separation in the grain, it would be magnified on the surface.  Bummer isn't it.


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## chriselle (Nov 5, 2008)

Thank you for the thoughts guys.  This kokutan is so dense and hard that it's almost "grainless".  It's like a rock to turn..lol.  I think Rick is right on that I may be overdoing it with CA. ...this isn't a candy apple base coat/ clear coat hotrod...lol.


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## mrcook4570 (Nov 5, 2008)

A cross cut blank would explain the direction of the crack.  Some woods may crack several months after making the pen.  Whether it is due to excess moisture in the wood before turning, humidity changes, or other stress, I do not know.  However, I have noticed it more frequently in cross cut blanks.  Cross cut blanks have a much larger area of exposed end grain than straight cut blanks, so this would allow more movement with changes in humidity.


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## Skye (Nov 5, 2008)

How do you press the kit together?


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## mrcook4570 (Nov 5, 2008)

chriselle said:


> This kokutan is so dense and hard that it's almost "grainless".  It's like a rock to turn..




Sounds like it may be very similar to ebony, which is noted for cracking months after it was turned.  As for overdoing it with CA, I don't think that is possible.  It may be possible to be too aggressive with sanding it afterward and building up heat which could contribute to the cracking issue.


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## SuperDave (Nov 5, 2008)

A crosscut grain will expand from top to bottom at a much larger percentage than side to side. CA is not a flexible finish, so depending on the percentage of expansion or contraction, the CA finish could crack without the wood grain itself separating.

Typically, in the finishing arena, it has been a long held belief that both sides of a wood panel need to be finished equally to avoid one side moving more than the other. Is this at work in your case? Hard to tell. I would suspect, however, that humidity is moving in from the barrel ends of the pen, causing the crosscut body to expand or contract top to bottom.

Lastly, depending on what part of the tree the wood came from, branch vs. trunk, etc. you can have "stress wood." After cutting and turning, the wood releases stress in the fibers, causing the finish to crack. On larger pieces of stress wood (panels, bowls, etc) you would typically get cupping or cracks in the wood itself. However, given the typical wall thickness of a pen body, I would suspect the wood to remain intact and a non-flexible finish could crack at the point where undue stress was released.

...or it could be Pen Gremlins


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## chriselle (Nov 5, 2008)

SuperDave said:


> A crosscut grain will expand from top to bottom at a much larger percentage than side to side. CA is not a flexible finish, so depending on the percentage of expansion or contraction, the CA finish could crack without the wood grain itself separating.
> 
> Typically, in the finishing arena, it has been a long held belief that both sides of a wood panel need to be finished equally to avoid one side moving more than the other. Is this at work in your case? Hard to tell. I would suspect, however, that humidity is moving in from the barrel ends of the pen, causing the crosscut body to expand or contract top to bottom.
> 
> ...



Very good point Superdave.  I've worked with quite a few carpenters here in Japan and one topic that often comes up is wood movement in the violent swings in humidity between the summer and winter.  Maybe I'm going to have to re-think my reluctance of using poly as a viable finish..lol.  

On your second point...I used to do some laminate work so the same premise as applying a backer to the substrate to avoid cupping.  

And yes,  gremlins could be a factor.


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## chriselle (Nov 5, 2008)

Skye said:


> How do you press the kit together?



With care....On the drill press.


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## leehljp (Nov 5, 2008)

A related side note here for the few that will read this at the end of a post:

Wood Expansion / Contraction:
Ever notice how even a barely used hammer head will come loose from the wood handle? 

Most people assume that it is because the hammer has been used a lot and the wood has just worn loose. Not so in all cases because it happens on hammers that have not been used at all. If a hammer is placed in a shop or barn without humidity control - in an environment with lots of seasonal humidity changes, - then over 4 to 5 years, the hammer head can become loose without it ever being used.

The reason is because of contractions / expansion phenomena. With high humidity, the wood expands within the steel head and is very tight. Then at low humidity times, the wood contracts. Again and again this happens. Gradually, the expansion cycle *crushes* the cell walls, layer by layer, with each cycle to the point that they cannot and do not recover. Once this starts, the inevitable looseness begins.

Until this is understood, the power of humidity in wood is easily overlooked. In Chris's picts and situation above the obvious strength (or weakness) of CA is displayed. Humidity changes affect most wood in certain directions more than in other directions and it did on this pen. Steel heads and rings (brass too) prevent expansion of shanks but also lead to crushed cell walls. IN the case of CA, - CA nor any finish is a match for the power of humidity in certain situations, unless the finish is flexible.

Another aspect of this is the density and flexibility of specific woods. Some woods can be constrained from expanding and contracting with less force better than others. Some woods that crack easily can be made into veneer as thick as 1/4 inch (6mm) without a problem while others cannot be made any thicker than 1/16 inch (2mm). Why don't veneers contract, expand and or crack like regular wood boards? There is a certain thickness related to individual woods in which treatment with finishes and glues can be effective. In the case of pens, Pen wood thickness is at the approximate level in which wood movement can be arrested - in most cases with the underlying glues and overlaying finishes. But generally, the denser the wood, the harder it is to control or fit the pattern of veneer expansion/contraction control, especially in cross cut woods.

It is my contention that easily cracked hard woods such as ebonies and snakewood will be aided by gluing them to the tubes with a rubber adhesive which will allow for contraction and expansion that CA and Epoxy do not. But for the finish - how do you add a flexible finish?  :wink:


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## NewLondon88 (Nov 5, 2008)

leehljp said:


> But for the finish - how do you add a flexible finish?  :wink:



Flexible CA?


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## leehljp (Nov 5, 2008)

NewLondon88 said:


> Flexible CA?



The only flexible CA that I have seen is black.  :bulgy-eyes:  :biggrin:


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## chriselle (Nov 6, 2008)

Thank you for the thorough insight Hank.  A poly finish should have enough flexibility and I do have a bunch of automotive clear coat I could load up easy enough in an airbrush and shoot.


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## leehljp (Nov 6, 2008)

chriselle said:


> Thank you for the thorough insight Hank.  A poly finish should have enough flexibility and I do have a bunch of automotive clear coat I could load up easy enough in an airbrush and shoot.



That hammer illustration is from R. Bruce Hoadley in his book "Understanding Wood" page 128 - 129. :biggrin:


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## MobilMan (Nov 6, 2008)

Chriselle.  I've just gotta ask.  Who is that beautiful little gal in that picture?  I'm guessing a daughter, right?  She sure is a cutie.  What's her horses' name.


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## chriselle (Nov 6, 2008)

MobilMan said:


> Chriselle.  I've just gotta ask.  Who is that beautiful little gal in that picture?  I'm guessing a daughter, right?  She sure is a cutie.  What's her horses' name.



Yes, she is my little angel.....daughter.  She definitely has her mother's good looks.  The way time flys...I'm sure it won't be too long before the young boys start coming around....argh!  Anyone got a salt gun for sale??:biggrin: 
No horse......YET!


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## Larry Gottlieb (Nov 6, 2008)

I had a few pens that developed circular ridges immediately after I assembled them. Since I make the blanks longer than the tubes (1/8-1/4"), I wondered if I was compressing the wood in assembling the pens.

I now use a lighter touch and have not experienced this.

By the way I use BLO/CA with 3 coats of CA.

Larry


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## TellicoTurning (Nov 8, 2008)

I've had a couple of cross cut blanks that crack the CA finish.. one was a really nice Australian burl that cracked cross wise.. much more than a hairline.. enough separation that you could see the tube through the crack.  I was disappointed, but just figured the wood wasn't completely dry when I made the pen and continued to dry and contracted to create the crack.


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## RussFairfield (Nov 8, 2008)

Everyone using CA glue as a finish will eventually have a cracking experience. Cracking of some type is a fact of life because the wood is a dynamic material and the CA glue is not.  

All wood moves with changes in humidity and temperature, some more than others, and in some directions more than others. CA glue, on the other hand, is a brittle material that doesn't move with changes in humiodity. It also becomes more brittle with age, and shrinks with age. 

These cracks are usually the result of the wood moving and the finish not. We always say there is no movement in the end-grain direction, but this is not true. While most species have very little movement, it is never Zero, and some of the exotics can have greater than 1% movement in the end-grain direction. .

CA glue, is just the opposite from the wood. It is a brittle material that changes very little with temperature changes and not at all with changes in humidity. As a brittle material, CA glue handles compression fairly well, but has essentially no ability to be stretched with wood movement. To make the problem worse, CA glues become more brittle with age, and they also shrink with age; and these are the reasons why the cracks always seem to happen some time after it was applied as a finish.


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## chriselle (Nov 8, 2008)

RussFairfield said:


> Everyone using CA glue as a finish will eventually have a cracking experience. Cracking of some type is a fact of life because the wood is a dynamic material and the CA glue is not.
> 
> All wood moves with changes in humidity and temperature, some more than others, and in some directions more than others. CA glue, on the other hand, is a brittle material that doesn't move with changes in humiodity. It also becomes more brittle with age, and shrinks with age.
> 
> ...




Thanks Russ.  In all the pens I've made this is only the second incidence of cracking so really it is rather insignificant.  I am re-thinking my finishing techniques for pens that I make in the humid months.  The shift between very high humidity to low humidity is also very fast and that is when I noticed the cracks on both pens.  As I said in a previous post wood movement is serious concern with woodworkers but here I just never applied that thinking to a pen.  
  It's interesting to note that both pens were euros and if you leave them a little fat (I do) they tend to have the thickest wood of any kit I turn.


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## Skye (Nov 12, 2008)

chriselle said:


> Yes, she is my little angel.



Not to alarm you but.... SOMEONE STOLE YOUR STEERING WHEEL!


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## NewLondon88 (Nov 12, 2008)

Skye said:


> Not to alarm you but.... SOMEONE STOLE YOUR STEERING WHEEL!



LOL ..  I should have put down the ginger ale before reading that.
It came out my nose


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## chriselle (Nov 12, 2008)

Skye said:


> Not to alarm you but.... SOMEONE STOLE YOUR STEERING WHEEL!



Yes, and they did an admirable job of covering up the crime with a glovebox.

Well, by all accounts here on the IAP, you should be considered the prime suspect.:tongue:


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## RMB (Nov 22, 2008)

The grain orientation explains it... wood expands and contracts far more acrost the grain than with it. Doing a lot of flatwork, I've seen it happen. That's the reason for floating panels in wide solid wood doors.


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## GouletPens (Nov 23, 2008)

I've recently had this problem with a pen that I made, though I don't use a CA finish (am I the only one????). I live in central VA and we have the wild swings in humidity as well. I was wondering if maybe there's some kind of humidor I could build to store my finished pens in? I try to use humidifiers to control the RH, but when it swings from 65% to 31% in a week, what can one do?!


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## leehljp (Nov 23, 2008)

Most woods that will be used as a cross grain cut should be stabilized in a pressure pot with something like acrylic/acetone, MEK or other. 

Thin laminates and veneers do not usually crack or move because of the thinness and adhesive. At some point movement can be overcome with the right saturation/stabilization and pressure relative to wood thickness. Basically when the cells become plasticized.


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