Official Luthiers Forum!

Hello,
This is my first time post here. I build a ziricote S&B + Italian spruce top drad one year ago, my customer complain that back finish is start to crack. I took it back than sand it down and refinish it with french polish. And today I got the mail said the back still crack again.
Is this a common problem on ziricote? And is there any good solution for it?


This is the pic the guitar first time finished. Not really sure waht's wrong with it. Hope you guys could give me some input, thanks

Hi Kan-Hung and welcome to the OLF!

Before attempting to diagnose why the guitar is cracking we would need to know more about how you built it. Here are some of the questions that come to my mind:

1) How well seasoned was the Ziricote before you used it for this guitar, how long had you had it, how do you store your wood, etc?

2) What kind of humidity control do you have in your shop including the range of relative humidity that you keep your shop at?

3) What is the climate, relative humidity wise, that the customer keeps the instrument in?

4) Where are the cracks exactly?

Thanks. Ziricote is known to be crack-friendly.... and has been called on this very forum Mexican Crack Wood before. It may not be something that you did or did not do or it may be a contributing factor. Once we know more I'm sure that folks here would be keen to help you.

Welcome again

Following this one closely as i hopefully will be starting the finish on my first Ziricote body shortly.
Details please!

Enquiring minds wanna know...

Ziricote is noted for cracks as Hesh has stated. I like to flood with thin CA as a precaution. Some cracks are invisible but the thin CA will be drawn into the cracks if there are any and you will see the glue on the opposite side. If no cracks then no harm done.

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And the CA has no effect on the bonding of finish? I am assuming that you would not have suggested it if it wasn't so, but just want to be certain. I am pretty sure that's the case with varnish (according to my converstions with Al) which is likely to be the finish on my project.

Al Carruth showed me a test strip of various finishes and they way each one enhances (or not) the grain. A major factor being the refraction index(?) of the cured finish.

I am wondering:
- Would adding a layer of CA would defeat that?
Al's test was on mahogany which you all know has great chatoyance. The varnish he had greatly enhanced that compared to other types of finish. The raw Ziricote i have is kind of dull (due to the oils?), so i want to make sure i maximize the effect a finish has.

- If i use thin CA, will it only be absorbed into the cracks and the rest of the area will be scraped off? I am guessing not. That a certain amount will be absorbed and i'll have CA impregnated wood. Is that... less than desireable?

- Would i be better off using a liberal dose of denatured alcohol to see if there are leaks first? Or would that lead to swelling of the woods and cause it's own problems?

- Is the purpose of the CA to fill the cracks or to hold the darn thing together? Would several coats of thinned varnish serve to do the same thing?

This is a bit like having my first kid, running through that sense of panic... will my child be born with everything intact?

Bob many folks use CA to pore fill without any ill effects. The CA would repair the cracks as well as seep into the pores. You wouldn't scrape it off but sand it as you go about your normal build sequence. t's only a very thin layer applied with either a single edge razor blade or an old credit card. Wear protective gear. Stuff really makes my eyes burn. Most first time builders or those with only a few builds have a tendency to worry too much. Relax and enjoy building.

_________________
Beautiful and unusual tone woods at a reasonable price.
http://www.rctonewoods.com/RCT_Store
The Zootman
1109 Military Rd.
Kenmore, NY 14217
(716) 874-1498

Too close to the end to screw it up now!

Peace of mind dictates i'm going to have to try it on the cut offs...

Thanks you guy for lot of inputs.
I will make things more clearly.

1) How well seasoned was the Ziricote before you used it for this guitar, how long had you had it, how do you store your wood, etc?
I bought the wood from LMI and store it for one year before I start to work with.

2) What kind of humidity control do you have in your shop including the range of relative humidity that you keep your shop at?
I have a room with humidity control to store all my woods, it always around 55 to 60 percent of humidity in the room. Due to Taiwan is really wet so it's hard to get the percentage lower.

3) What is the climate, relative humidity wise, that the customer keeps the instrument in?
This is the think I really not sure, but I can tell you here in Taiwan is very wet and the humidity percentage is around 65 to 85 percent.

4) Where are the cracks exactly?
The cracks is near the center line of back board but not at the dead center, I'll make some pics for it.

One thing I forget to say is the first time I sand the finish down. I found some small wood cracks and put some CA glue on them. It will fix the the problem in my experience, but it's not.

Thanks again

Rob like Bob said.On crack friendly wood like Ziricote and Brazillian,I shoot a coat of shellac and then flood with CA.Then sand it off .I also pore fill with CA later in the build sequence.Kind of a double wammy.Then before applying finish I shoot a couple more coats of shellac and all is good.

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James W Bolan
Nashville Tennessee

Hello folks,
I get some pics from the customer. The cracks looks crazy. I'm just wondering is it worth to repair or I just rebuild one.

You could try to repair one crack at a time by applying CA and immediately sanding the wet glue making a slurry that is being forced into the crack by the sanding pressure. Then move to the next crack. You will have to sand and refinish after the repairs are done.

_________________
Beautiful and unusual tone woods at a reasonable price.
http://www.rctonewoods.com/RCT_Store
The Zootman
1109 Military Rd.
Kenmore, NY 14217
(716) 874-1498

Thats unfortunate.... And that wood looks so much like mine... *sigh*

Do those look like the typical types of cracks that ziricote seems to be noted for? or do those look more humidity related ... or just a natural bad place... ??

Ziricote usually cracks along the black grain lines, but it does like to crack. I built with it and braced at the lowest RH possible, around 20%. So far, it has held up nicely. There were two long cracks on the back that I filled and then put patches on, but they were there before I began building. They have also remained stable.

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PMoMC

Lame joke alert: There are two types of ziricote; ziricote that has cracked, and ziricote that is going to crack.

I love the stuff, both its look and its qualities as a tonewood, but as has been said, it sure likes to crack. I drench both inside and outside with thin CA, and pore fill with medium CA, so far so good. I like to build in a drier %RH than what my instruments will normally see, to account for the few months of the year where it gets drier than it was when the instrument was braced, which is when most cracks happen. It sounds like you did pretty much the same, but perhaps the instrument was taken somewhere the RH is lower, or perhaps this is just a piece of wood that is particularly prone to cracking, who knows. I would humidify the instrument so the cracks close, repair with CA or thin hide glue, and instruct to owner to mind the RH in the future. Perhaps it will hold up...

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Rian Gitar og Mandolin

I am hoping, since i had my wood for 6 years or so, that i may not have these issues?

You can always hope... It's no guarantee, I'm afraid. I'd still take all the usual precautions

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Rian Gitar og Mandolin

I'll likely do the flooding the B/S with thin CA. I had thought about sealing them with shellac on the inside but hesitated due to future repair considerations, but i am second guessing that now. Box is closed so it's not easily an option now.

I had bout my first bottle of CA at Home Depot. Small bottle not much larger than a fingernail polish bottle. How much would i need for a typical guitar... I am thinking i may be better off going to a hobby shop for thin CA?

Hi,a friend of mine built a Ziricote guitar 25 years ago, and so I have seen how they can crack.On his,both sides cracked badly and the back split open in several places,almost splintering in one area.The wood was well seasoned and the guitar skilfully made.Although he has more sets,he hasn't built with it since.I have a well seasoned set,that I've had for years.Every year or so ,I pull it out to check it,and there is always another crack,although minute,which gets the superglue treatment.The cracks never open,once glued,but more, occasionally appear.When I eventually do use it,it will be well sealed ,on the inside,and all edges.Our wood came from different sources at different times.It is a very unstable, but beautiful,wood,and can give a great tone,even when cracked.I think its all down to luck.I'm sure there are people here that built with it ,years ago and have never had problems.

This has proved to be a helpful topic to me as I am soon to begin my first build with Ziricote.
Question: I'm thinking of flooding the back and sides with CA prior to thicknessing to stabilize all those invisible weak spots. Pros? Cons? Remember, there are no stupid questions, just stupid people who ask good questions.

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Doug

Don't let fear or common sense stop you from trying to build something

...or would pore filling with thin epoxy help significantly?

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Doug

Don't let fear or common sense stop you from trying to build something

No, that will not prevent the cracks. Epoxy sits on the surface, thin CA actually wicks into the wood.

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Brian

You never know what you are capable of until you actually try.

https://www.howardguitarsdelaware.com/

Finally back to this thread,
After a long run discussion, I mention that all the possibility and no guarantee for the crack will happen again. My customer ask the full refund then this case just finished.
I think I would not use ziricote for build for a while, till I can make sure everything will be good
At least I have a guitar sounds and looks really cool for myself.

Thanks for you guy giving so much information, that really help.
I appreciate for it.

Mine also cracked during finishing. Stupidly i could not get the varnish to dry and cranked up the heat not thinking what that would do to the humidity. Over several weeks i ended up with 5 cracks! Ugh! in the end, i sanded down to the wood and flooded the cracks with CA (sometimes more than once!) I eventually used 5 coats of shellac as it was the only way the varnish would dry. I don't know if the finish would have been better with pure varnish but it wasn't an option and i am totally happy with the result... The guitar should finally be complete next weekend and i'll be posting pics then..

Don't think i would use ziricote again unless i was fanatical about the humidity for the remaineder of the guitar's life... but certainly if i ever build one for sale there's going to be a cracking clause on the thing.

That's too bad because it sure is a beautiful looking guitar. I'll probably never use the stuff based on the stories like this that I hear. But it is nice looking stuff, probably best for laminate back and sides.

Might it be a good idea to coat the inside with shellac if building with this type of wood ? Sorry if off topic.

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