Cracking finish

[kentonjm]

I have noticed in a couple of pens I finished more than a month ago that the CA finish seems to have cracked. I can see visible spiderweb lines that look like somebody smashed a plate window.

What can have caused this? How do I avoid it in the future?

 

[Dalecamino]

Extreme change in temperature. Either, hot or cold. I had my zippered case of pens with me in a bar where my daughter worked, one December night. After showing my pens, I took the case out to the car for a few hours. Next day, they were all cracked. A friend of mine in Florida, left his pen I gave him in his car. It also cracked.

Someone said, the brass tubes expand in cold temps.

 

[JimB]

The wood might not have been completely dry so it continued to dry after you finished it. The wood moved and caused the cracks. Sometimes, with some woods, just the turning process can relieve stresses and cause wood to move.

 

[leehljp]

A fellow from Japan who used to be here had some crack in his display case in his store. It wasn't really hot but still it got direct sunlight for a short time each day in that one spot. Cracked finish. I think that was back in '08 or '09.

Heat will do it; So will sneaky people who use it when you aren't looking. DAMHIKT :biggrin:

 

[terry q]

How old is your CA? I had a bunch of failures and realized my CA was about a year old.

 

[jttheclockman]

Jon, there are many reasons why it may have happened. There are things to try to do to prevent it. But does it ever stop with any of the fixes, no one can guarantee this. There are those that say the type CA used is the answer where CA glues that are more flexible can withstand this movement. There are those that say the use of accelerator will harden the CA too fast and cause it to become brittle. I happen to fall into that catagory. But scientific proof of any of this is not there. I highly suggest you fill the search box above with some of those key words and you will get a ton of past threads that will keep you busy reading for awhile and if you can take something out of them that may help you then it is not a waste of time. Good luck.

 

[Skie_M]

I have, thankfully, never had an issue with my CA finish cracking yet. I use those disposable little tubes all the time ... I pick them up from Harbor Freight every time they offer a coupon for free tarp with purchase or something else I could use. I justify it as "Ok, I'm buying a tarp and I get 30 free superglue tubes" or something ... and I can always use spare tarps!


I think that the cracking issue can be traced to one of several root causes -

Extreme temperature change.
When wood is heated up, it can expand a little ... metal expands a bit more ... acrylic expands less. CA is acrylic and it's a pretty weak thin layer trying to stop that expansion.

When wood is frozen, it can expand a lot, from the water that may be trapped inside. In extremely cold areas of the world, it's not uncommon to hear something like a gunshot out in the woods and find a tree trunk that has EXPLODED from the freezing sap inside. If there is a lot of moisture in your pen barrel, it can cause it to expand a good bit, and the acrylic would try to shrink - not a good mix.

Improper use of accelerator can also cause issues, as the polymerization is sped up, it may not have time to properly form bonds and longer chains for additional strength. I don't use accelerator at all.

Improper sealing of the pen barrel can cause many issues. If you don't seal the ENDS of the pen barrels, top and bottom (just the wood part), then environmental moisture can infiltrate the wood, causing the issues mentioned above.


Make sure your customers know that these are HAND MADE pens, crafted of wood, and that wood can be unpredictable. As craftsmen (and women), we will do all we can to preserve that beauty for the ages, but the future of that item is LITERALLY in the hands of it's owner now, and proper care is of high importance.

"Please do not leave in hot places (over 100 degrees) or cold places (below 20 degrees), do not freeze, do not submerge, do not microwave, and please do not chew!"

 

[kentonjm]

How old is your CA? I had a bunch of failures and realized my CA was about a year old.

I have various ages, some is new others could easily be over a year old.

 

[kentonjm]

Of all the possible issues mentioned I think the use of accelerator seems the most likely. I am still pretty new to the whole pen and CA finish method. I think it is highly possible that I have overdone the accelerator.

I have a few different thicknesses and brands of CA glue. Some are the Stick Fast CA finish which seem to take much longer to set and I find myself using more accelerator as impatience sets in. These CA finish bottles came with the whole setup that I bought from somebody last year so I have no idea how old they are but they must be at least 12-18 months. I dont really like them so I think I will stop using those and reserve them just for filling holes and other general CA glue type jobs.

I quite like the BLO + CA approach but I really dont know how many coats I have to use doing it that way and I am not sure whether you need to keep using the BLO after the first 4 or so coats as by that time there is no wood for the blo to soak into. Also I have had a few examples of sanding/polishing through the CA when I start to use the micromesh so I then go back and probably put too thick coats on through frustration.

I know this is a learning curve but I would love to be further up it

 

[edstreet]

Why are we doing a witch hunt and finger pointing when the problem is relatively simple?

 

[Dalecamino]

Jon, I was wrong about the time of year this happened. Before you pin the problem on any particular thing, you might read through this thread.

http://www.penturners.org/forum/f18/cracked-hrb-77227/

 

[Bill in Buena Park]

Jon, I think your conclusion about the accelerator being a factor is correct. Although rare, I've had the "cracked glass" happen a time or two as well (so there are likely other factors involved, like CA layer being too thick and not fully cured before starting the next layer). It also happens I was using the Stick-fast accelerator at the time.

Following the link in EdStreet's note (below sig line) to Toni's site showed an article with a list of "good" accelerators, one of which is the BSI (Bob Smith) brand. To my surprise, the new accelerator I recently ordered from Penn State (PSI) - their "Insta-set" - is made by BSI - which I found through the MSDS on the PSI webpage. I haven't used it yet, but hope it yields great results.

 

[efrulla]

On the accelerator issue I fall in the middle. My technique is to apply 3 or 4 coats of thin initially and let each coat cure without the accelerator. My way of thinking is that the thin will wick into the wood and the long cure time allows for stronger bonding. I then move to medium CA and accelerator to put on another 9 coats. I have not had any experience with this cracking but I also have never exposed any of my pens to extreme temperatures yet. Just my 2 cents for what it is worth.