Trouble with CA cracking

[Uncle_Lou]

Hello! New to the forums and still rather new to turning, hoping to learn some things here. I know this forum is focused on pen turning; my question pertains to bottle stoppers but I have to imagine the theory and techniques are similar enough to bear on my issue.

So the CA finish on virtually every stopper I have turned recently has cracked within anywhere from an hour to a couple of days after applying it. I am trying desperately to figure out if it is the product or the application so that I can avoid having to redo my work. I have been doing what research I can to try to narrow down cause, and finally decided it might be faster to simply ask those who know better than I do.

Everything I can think of that is relevant:
-My stepdad (owns the lathe and work space) stores his CA and other supplies in an un-insulated garage. Being in Western NY, on cold days the interior of the garage can get down close to freezing if not below on the really brutal days.
-We have been using Stick Fast Thin CA on these products. I'm not sure how old the bottle in question is, the bottle is nearly empty so it could potentially be older than 6 months or even a year.
-For application I typically will do 8-10 thin coats of the Stick Fast Thin with a quick shot of Accelerator between each coat. This is the method my stepdad uses for his pens, and he doesn't seem to have any issues with the CA cracking.
-The cracks mostly seem to start in an area where there is an edge or a smaller radius curve in the blank, then propagate slowly through the rest of the finish.
-The cracks do not appear to reach the surface of the finish but are rather in the inner layers.

So I'm not sure if I need to try a newer bottle (we are also looking at GluBoost as an alternative), or give the Stick Fast more time between coats. I've also been speculating that with the larger amount of blank material in a bottle stopper that the Thick Fast Thin may not be flexible enough to handle any movement of the blank material after application.

I appreciate any thoughts or suggestions that anyone may have. I really enjoy creating these pieces but the finish is driving me nuts. Every time I think I have completed a piece and the finish is beautiful, when I look at it later it is spidered with cracks. I can provide photos if it would be helpful. Thanks!

 

[Monty]

IIRC several years back there was a problem with Stick Fast cracking on pens.
Don't know if it still is. I had used EZ Bond until a few years back. I now use Glue Boost.

 

[jttheclockman]

For bottle stoppers I would not use CA. I would use a poly weather wipe on or a spray on. Do not use brush on. Normally I would say to use lacquer on just about any other object like that but being of alcohol content that would eat into the finish. This is just my opinion. Stick fast has been known to cause problems even with pens and seems to be date sensitive as well as storage sensitive. CA dries brittle and wood moves. You are now using a larger mass of wood compared to a pen. So means more movement. Good luck.

 

[Mortalis]

I don't like to use accelerator whenever I can avoid it. Personal preference.
If all you're using is thin then I dont see a reason to need to use accelerator as thin dries within seconds of application unless you are applying the CA too thickly and it isnt drying quickly enough for you and then in lies your problem most likely. CA applied too thick then accelerated could cause issues if it continues to cure underneath the next coat.
Grasping at a lot of straws but I've never encountered the issue using CA. BTW, I use Bob Smith Industries CA.

 

[1080Wayne]

Cracks starting at the smallest radius , makes me wonder if the wood is dry . In my opinion any turning of that diameter needs to be @ 5-6 % MC to minimize CA cracking . John`s suggestion to use a different finish would be my approach .

 

[jrista]

I haven't tried GlueBoost yet, but I did switch from StickFast (which causes me severe respirstory problems) and other CAs to Mercury Flex. I still get breathing issues if I am exposed to Mercury CA, but...the flex stuff doesn't dry as brittle hard as normal CA glues. It is still harder and durable, but I think it still gives the wood room to move a bit. I don't know if it would handle the amount of movement you are getting with your stoppers, but it might be worth a try.

 

[Uncle_Lou]

For bottle stoppers I would not use CA. I would use a poly weather wipe on or a spray on. Do not use brush on. Normally I would say to use lacquer on just about any other object like that but being of alcohol content that would eat into the finish. This is just my opinion. Stick fast has been known to cause problems even with pens and seems to be date sensitive as well as storage sensitive. CA dries brittle and wood moves. You are now using a larger mass of wood compared to a pen. So means more movement. Good luck.

I appreciate all of the responses. Forgive my ignorance - as I said, still relatively new to this. When you say poly, are you referring to something like a Minwax polyurethane finish? If so, that seems like something that would take a fair amount of time to cure. Can it be polished afterward?

Not sure how to measure moisture content in the wood prior to finishing, but I expect it is quite a bit higher than 5-6%.

It also sounds like a more flexible finish like GluBoost or Mercury Flex might yield better results?

Thanks again!!

 

[BULLWINKLE]

For bottle stoppers I prefer to use stabilized wood blanks or acrylic. I wet sand down to 12,000 micromesh. No finish needed on either material. Problem solved and less work for me.

 

[jttheclockman]

Hello James and welcome to the site. First and foremost you are not the first to ask about finishes on stoppers and there are threads here that go back quite afew years and the choices of finishes are as wide spread as they are today. Here is my thoughts and mine alone. When dealing with stoppers you have a couple problems and it depends how they are used and on what. First is alcohol. Not good for shellac and lacquers. Never tested against CA. Just not a fan of using CA on anything other than small round objects like pens or needle thingys. The next problem you run into is hot and cold and condensation from in and out of fridge. people forget to take that into consideration. Nick a stopper from use and it will destroy CA. Just ask the many who complain about moisture getting under their pens finish when they wet sand. Plus like I said CA is brittle and if you are using accelerator, this makes it even more brittle because you are forcing the off gasing and drying process. Plus if a layer is not dry under your next layer it can ghost on you and show up cloudy.

I will try to keep this as short as possible but be thorough. People use brush on or spray lacquers and yes they are very quick and each layer basically melts into each other making them a nice finish to build with and no polishing is needed. Usually the more coats the deeper the look is. But again alcohol can break down that finish.

This is why I suggest a harder finish but also stays somewhat flexible and also can withstand temp changes. No polishing is needed but can be applied if you feel a need. But any polish or hand rubbed finish will wear off very quickly. Unless these stopper are for decoration. People have used a finish called Enduro and it is a poly mix and is a very good finish for pens as well as stoppers. Some people is they use exotic woods will just use a Danish oil and then polish and it brings out a nice wood feel and semi gloss shine.

Now of course the best stoppers are acrylic. No finish and just treat like a pen.

But for me I would use a wipe on poly such as minwax. I am a huge fan of Formbys. My entire woodwork and doors are finished with this and wipe-on was the way to go. Easy to apply and additional coats is a matter of knocking any dust specks off with a nonwoven pad. I use the grey ones. Clean off and add second coat. Now you are falling into the same trap as many here when they talk about speed. If you want fast then get out of this hobby. Your end product will suffer. We want to produce items that are above and beyond store bought cheap junk. I cringe when people talk about time to apply a coat of finish. Learn to do your pens stoppers and whatever in bunches and work as if an assembly line. Do not force any steps. This is my opinion and I gave you my best response. If you stick with CA then I suggest try a different brand and if using accelerator make sure it is compatible to CA. One size does not fit all. Good luck and show us some of your work.

One thing I should have mentioned try to stay away from sharp edges when designing shapes. Not good for any finish.

 

[Bope]

John, are your talking about General Finishes Enduro line of products? I use their Enduro Exterior 450 on tack trunks all the time. Thinking about a bottle stopper going in and out of a refrigerator this finish makes sense. I have not tried using it as a wipe-on product. Being waterborne you can't do as much dilution as an oil based varnish to thin it our for wiping. I spray it on the tack trunks.

 

[wouldentu2?]

I haven't tried GlueBoost yet, but I did switch from StickFast (which causes me severe respirstory problems) and other CAs to Mercury Flex. I still get breathing issues if I am exposed to Mercury CA, but...the flex stuff doesn't dry as brittle hard as normal CA glues. It is still harder and durable, but I think it still gives the wood room to move a bit. I don't know if it would handle the amount of movement you are getting with your stoppers, but it might be worth a try.

I had the breathing issues 12 years ago and switched to BSI super gold which is odorless and never had another problem. Probably do 150 pens a year and apply it 1-2 drops at a time on craft foam which does not absorb the CA. Better finish and no wasted CA because it is more expensive than other types.

 

[MPVic]

Hello James and welcome to the site. First and foremost you are not the first to ask about finishes on stoppers and there are threads here that go back quite afew years and the choices of finishes are as wide spread as they are today. Here is my thoughts and mine alone. When dealing with stoppers you have a couple problems and it depends how they are used and on what. First is alcohol. Not good for shellac and lacquers. Never tested against CA. Just not a fan of using CA on anything other than small round objects like pens or needle thingys. The next problem you run into is hot and cold and condensation from in and out of fridge. people forget to take that into consideration. Nick a stopper from use and it will destroy CA. Just ask the many who complain about moisture getting under their pens finish when they wet sand. Plus like I said CA is brittle and if you are using accelerator, this makes it even more brittle because you are forcing the off gasing and drying process. Plus if a layer is not dry under your next layer it can ghost on you and show up cloudy.

I will try to keep this as short as possible but be thorough. People use brush on or spray lacquers and yes they are very quick and each layer basically melts into each other making them a nice finish to build with and no polishing is needed. Usually the more coats the deeper the look is. But again alcohol can break down that finish.

This is why I suggest a harder finish but also stays somewhat flexible and also can withstand temp changes. No polishing is needed but can be applied if you feel a need. But any polish or hand rubbed finish will wear off very quickly. Unless these stopper are for decoration. People have used a finish called Enduro and it is a poly mix and is a very good finish for pens as well as stoppers. Some people is they use exotic woods will just use a Danish oil and then polish and it brings out a nice wood feel and semi gloss shine.

Now of course the best stoppers are acrylic. No finish and just treat like a pen.

But for me I would use a wipe on poly such as minwax. I am a huge fan of Formbys. My entire woodwork and doors are finished with this and wipe-on was the way to go. Easy to apply and additional coats is a matter of knocking any dust specks off with a nonwoven pad. I use the grey ones. Clean off and add second coat. Now you are falling into the same trap as many here when they talk about speed. If you want fast then get out of this hobby. Your end product will suffer. We want to produce items that are above and beyond store bought cheap junk. I cringe when people talk about time to apply a coat of finish. Learn to do your pens stoppers and whatever in bunches and work as if an assembly line. Do not force any steps. This is my opinion and I gave you my best response. If you stick with CA then I suggest try a different brand and if using accelerator make sure it is compatible to CA. One size does not fit all. Good luck and show us some of your work.

One thing I should have mentioned try to stay away from sharp edges when designing shapes. Not good for any finish.

John,
Always enjoy & value your input. You mentioned using Enduro as a good finish for pens. I notice several Enduro products on line - is there a particular one that you would recommend for pens? CA is slowly becoming an issue with my chronic bronchitis so an alternate would be welcome. In all the items you have shared in the past I don't recall what finishing process you favor when making wooden pens - would you mind sharing? Thanks.

 

[Jarod888]

I've never had any luck with stick fast CA glue.

Some things I would try.

1. Ensure your blank is dry. If the blank is wet or better said has a higher moisture content than the relative humidity in your area, it may be drying out and this shrinking. Also, because your issue originates from the smaller end of the bottle stopper, that end may be dryer than the thicker area and thus the blank is trying to equalize. You can always try the toaster oven method of drying. You need to raise the internal temperature of the blank above the boiling point of water. Once the blank has stopped losing weight, it is dry. It then needs to be kept in an air tight container; double ziplock bag with a silica gel pack works great, or a vacuum sealer bagging system is the best. Don't turn the blank when it is just out of the oven and don't dilly dally when prepping it. The goal is to turn and finish it before it can absorb moisture back into the blank. Wood will always try to equalize its moisture content to the relative humidity of the area you are in. The only true way to prevent this is to stabilize the blank. Stabilizing is the art of replacing the internal moisture with a substance that hardens and thus fills the pores of the wood, preventing them from holding moisture.

2. Your ca may not be fully cured before you apply your next layer. Thus, as it continues to setup underneath the layer above it, it shinks slightly and thus cracks. That is one reasons folks often recommend staying away from accelerator. It speeds up the curing process, but only at the very top of the ca, and the under layer may still be wet, so as it eventually cures, it can't move and thus cracks.

3. Your ca may be bad. CA has a shelf life and can be affected by use. Essentially, as you are using it, it is exposed to the atmosphere of your shop and can absorb moisture from the air. The microscopic amount of moisture won't cause it to cure, but it will alter the composition causing issues later as it is used.

4. The cold temperature in your shop is not a bad thing. The issue is actually related to the temperature swings. Several folks keep their CA in the refrigerator. They all say keeping it cold extends the shelf life.

5. Try a ca that has a flexible option. This allows the ca to move with the wood whichs assists with the cracking. Traditional CA is very rigid, so it doesn't move as the wood moves. Mercury Flex is wonderful. Be aware, you will need new accelerator with Mercury. It uses heptane based accelerator, rather than the acetone based accelerator most others use.

 

[sorcerertd]

It is cool to have the freedom of shape in stoppers, but it is also a pain in the butt to finish (as you have obviously discovered). To me, CA is hard to polish on something with lots of ridges because I usually end up taking off the finish on the "hills" and not getting as much polish on the "valleys" as I want. It's been mentioned, but bears repeating, that wipe on poly is a great bet for those. I can't say it is the best, because I have not tried them all.

That being said, I would definitely steer clear of stick fast. It's notorious for cracking and I can confirm that from experience. I have also switched to GluBoost. It costs more, but the results are much better. Gluboost is not marketed as a glue, but as a finish, and there is good reason for that. it some elasticity to keep it from cracking/crazing. Others have had good results with other products, but I'm going to "stick" with the CA that works for me. My only complaint about GluBoost is that the accelerator is crazy expensive for such a tiny can, although it doesn't cause bloom (the opaque, whitish spots).

 

[jttheclockman]

John, are your talking about General Finishes Enduro line of products? I use their Enduro Exterior 450 on tack trunks all the time. Thinking about a bottle stopper going in and out of a refrigerator this finish makes sense. I have not tried using it as a wipe-on product. Being waterborne you can't do as much dilution as an oil based varnish to thin it our for wiping. I spray it on the tack trunks.

John,
Always enjoy & value your input. You mentioned using Enduro as a good finish for pens. I notice several Enduro products on line - is there a particular one that you would recommend for pens? CA is slowly becoming an issue with my chronic bronchitis so an alternate would be welcome. In all the items you have shared in the past I don't recall what finishing process you favor when making wooden pens - would you mind sharing? Thanks.

Ok I see I have created some confusion. So I will try to explain and answer both these questions. First when it comes to me finishing wood pens I use Satelite City CA and have ever since I started making pens and will never change. Many here sing the praises of GluBoost as the finish of all times so maybe you need to try this. I will not because I have no need to change. If it is not broke don't fix it. I apply as many do with blue shop towels. I wet sand with MM and then add a coat of acrylic wax as final step. I love the sheen I get and have had no complaints from people who own my pens.

As far as the Enduro thing goes, (yes General Finishes) I was in a stage of trying different finishes for my scrollsaw projects years ago. I tried Enduro Clear Poly waterbased finish. It is best applied by use of a HVLP spray gun . You can look up the sheets on this finish and see it is possible to use brush and other methods. I have not tried them so can not speak of this. This was the finish back in 2014 that was being touted for bottle stopper by our own members here. You can search for those threads I am sure. people also talked about using on pens and in fact someone was selling small pint bottles here. I believe I still have somewhere. Many people loved this product but was time consuming to apply as I recall. For me I was happy with my CA for pens. I did dabble in some stoppers and wound up using that Enduro finish for them. They worked well. I never did pursue making them as a line of products so it has been awhile. For my scrollsaw projects I did not like the high gloss that the Enduro produced so I switched to a water based lacquer https://www.targetcoatings.com/product/emtech-em6000-wb-production-lacquer/.

Now getting back to topic about stoppers. I mentioned Enduro because it was touted here and is a polyurethane which is harder than lacquers. CA will give you problems as I mentioned above. This is fact. Some people their milage may vary but again their use of stopper maybe different. Other than Powder Coating I do not know of a harder finish that is also flexible enough to withstand the temp changes and abuse you can get from stopper use. Yes it takes longer to fully cure but water base cures faster than oils. Need to follow directions. There are so many of these type finishes and are just as durable. But again I will go back to my opinion and if I were to get back to making stoppers my finish of choice would be a wipe on poly (gloss) The problem with these are they are oil based so yellowing of lighter woods will happen. But ease of use is there. Use for pens I would not see a reason they can not also be tried. This is one man's opinion and I share what I know. Others may have different results using different products. But that is what forums are about sharing ideas. Good luck.

 

[Uncle_Lou]

Hello James and welcome to the site. First and foremost you are not the first to ask about finishes on stoppers and there are threads here that go back quite afew years and the choices of finishes are as wide spread as they are today. Here is my thoughts and mine alone. When dealing with stoppers you have a couple problems and it depends how they are used and on what. First is alcohol. Not good for shellac and lacquers. Never tested against CA. Just not a fan of using CA on anything other than small round objects like pens or needle thingys. The next problem you run into is hot and cold and condensation from in and out of fridge. people forget to take that into consideration. Nick a stopper from use and it will destroy CA. Just ask the many who complain about moisture getting under their pens finish when they wet sand. Plus like I said CA is brittle and if you are using accelerator, this makes it even more brittle because you are forcing the off gasing and drying process. Plus if a layer is not dry under your next layer it can ghost on you and show up cloudy.

I will try to keep this as short as possible but be thorough. People use brush on or spray lacquers and yes they are very quick and each layer basically melts into each other making them a nice finish to build with and no polishing is needed. Usually the more coats the deeper the look is. But again alcohol can break down that finish.

This is why I suggest a harder finish but also stays somewhat flexible and also can withstand temp changes. No polishing is needed but can be applied if you feel a need. But any polish or hand rubbed finish will wear off very quickly. Unless these stopper are for decoration. People have used a finish called Enduro and it is a poly mix and is a very good finish for pens as well as stoppers. Some people is they use exotic woods will just use a Danish oil and then polish and it brings out a nice wood feel and semi gloss shine.

Now of course the best stoppers are acrylic. No finish and just treat like a pen.

But for me I would use a wipe on poly such as minwax. I am a huge fan of Formbys. My entire woodwork and doors are finished with this and wipe-on was the way to go. Easy to apply and additional coats is a matter of knocking any dust specks off with a nonwoven pad. I use the grey ones. Clean off and add second coat. Now you are falling into the same trap as many here when they talk about speed. If you want fast then get out of this hobby. Your end product will suffer. We want to produce items that are above and beyond store bought cheap junk. I cringe when people talk about time to apply a coat of finish. Learn to do your pens stoppers and whatever in bunches and work as if an assembly line. Do not force any steps. This is my opinion and I gave you my best response. If you stick with CA then I suggest try a different brand and if using accelerator make sure it is compatible to CA. One size does not fit all. Good luck and show us some of your work.

One thing I should have mentioned try to stay away from sharp edges when designing shapes. Not good for any finish.

Thank you so much for all of this. You mentioned speed I assume as a response to my question/comment about cure time - I may have come across other than I intended. I'm not trying to rush any of this to completion; in fact as I've been learning I have been slowing down quite a bit as I have found (and it should have been obvious) that rushing any of this is going to yield poor results or generate additional labor. I've also been trying to compartmentalize the process; i.e. do only turning on one day, sanding another day, finishing another, etc. so I can focus better on that part of the process rather than bouncing around.

I will be honest I had not considered several of the points you mentioned with regard to use and temperature swings as a result and their affect on finishes. Might be worth my time to take a trip to the local hardware store and pick up a pint of rub on poly. Not sure why I didn't think of it; a long time ago I worked at Lowe's in the paint department. You mentioned yellowing with the poly on some woods; if memory serves Minwax makes a poly that cleans up with water. I believe it is supposed to be essentially waterproof once cured and doesn't yellow. Any thoughts?

With regards to sharp edges - already figuring that out! I have done a couple acrylester stoppers; I really like the results. If I do any corners/tighter radius curves in the future I will limit it to the acrylics as - in my head, at least - they should tolerate them better.

Thanks again for your time and insight. I have a tendency to dive into things feet first only to realize they are much less simple than anticipated, so all of the responses here are extremely helpful.

 

[jttheclockman]

Thank you so much for all of this. You mentioned speed I assume as a response to my question/comment about cure time - I may have come across other than I intended. I'm not trying to rush any of this to completion; in fact as I've been learning I have been slowing down quite a bit as I have found (and it should have been obvious) that rushing any of this is going to yield poor results or generate additional labor. I've also been trying to compartmentalize the process; i.e. do only turning on one day, sanding another day, finishing another, etc. so I can focus better on that part of the process rather than bouncing around.

I will be honest I had not considered several of the points you mentioned with regard to use and temperature swings as a result and their affect on finishes. Might be worth my time to take a trip to the local hardware store and pick up a pint of rub on poly. Not sure why I didn't think of it; a long time ago I worked at Lowe's in the paint department. You mentioned yellowing with the poly on some woods; if memory serves Minwax makes a poly that cleans up with water. I believe it is supposed to be essentially waterproof once cured and doesn't yellow. Any thoughts?

With regards to sharp edges - already figuring that out! I have done a couple acrylester stoppers; I really like the results. If I do any corners/tighter radius curves in the future I will limit it to the acrylics as - in my head, at least - they should tolerate them better.

Thanks again for your time and insight. I have a tendency to dive into things feet first only to realize they are much less simple than anticipated, so all of the responses here are extremely helpful.

James that is the way to attack what we do and also many projects. Make a plan and do as an assembly line. Saves time in the long run and the final product is worthy. Especially when doing glue ups and finishes.

Minwax and others make a waterbased wipe-on polyurethane, yes. Yes it cleans with water. Yes it will dry clearer but like any finish there will be some darkening and yellow tint. Not nearly as bad as oil and that is why they say clear. It still has some oil ingredients in it. The total down side with use a waterbased wipe-on finish it dries real fast and can become sticky and streaky especially if doing a large project. Thus the spraying comes into play. Now being such a small object as a stopper or pen you will be fine. Gloss will be a little thicker than satin so less coats. But with poly if you are doing more than one coat you need to sand in between and 400 grit to 600grit paper is fine. But as I said I like to use the nonwoven pads and use the grey ones for finishing. https://www.amazon.com/Non-Woven-Assorted-Abrasive-Peachtree-Woodworking/dp/B000H570E2 Now I say the yellowing effect for lighter woods. Unless you are using Aspen or Holly to me it does not matter. Woods like maple really stand out with that coloring effect you get with oils. Any other woods you never notice color changes. Gives a warm look in my opinion.

Thus I am a huge fan of oil based wipe-on finishes. Easier to work with, longer open time and flows real nice. Yes being a wipe on they are very thin viscosity so more coats needed. But with all finishes there are pros and cons. The perfect finish to me is always lacquers weather water based or Nitro. Still need to be careful of fumes and odors as with any finish. Protect hands with gloves, mask and good air flow. Not sure I can give any more details. Just need to practice with whatever finish you choose. You find your Rythm and method. Good luck.

I found this comparison report of the two finishes and it talks about pros and cons of each. Now I know this is basically talking about a floor finish but the same principles apply. But take a look at the photo of the floor with no finish in the middle and the two finishes on either side. Even the waterbased finish has some color to it. That is what I am talking about.

https://www.familyhandyman.com/arti...low odor.,day. ... 4 Cleans up with water too.

 

[leehljp]

I did not see it mentioned here and could have missed it. If you do a search for "cracked CA finishes", you will find a 2 to 1 or 3 to 1 ratio of cracked finishes with StickFast CA versus all others. I don't make lots of pens each year, but have been making them for 18 years, and with CA produced in two continents. The only one to crack for me has been StickFast. StickFast makes some good CA and CA itself is not or was not originally made to be a "finish", so I can't blame StickFast for cracking finishes, since they were not originally made for that purpose. However, very few of the other brands were made to be used as a finish, but happen to do well in the "finish" department without cracking like StickFast does.

I don't remember where I read it, (could have been someone here on IAP) but GlueBoost was formulated differently to be used as a finish instead of a glue. GlueBoost gets more compliments from its users than any other.

 

[Uncle_Lou]

I did not see it mentioned here and could have missed it. If you do a search for "cracked CA finishes", you will find a 2 to 1 or 3 to 1 ratio of cracked finishes with StickFast CA versus all others. I don't make lots of pens each year, but have been making them for 18 years, and with CA produced in two continents. The only one to crack for me has been StickFast. StickFast makes some good CA and CA itself is not or was not originally made to be a "finish", so I can't blame StickFast for cracking finishes, since they were not originally made for that purpose. However, very few of the other brands were made to be used as a finish, but happen to do well in the "finish" department without cracking like StickFast does.

I don't remember where I read it, (could have been someone here on IAP) but GlueBoost was formulated differently to be used as a finish instead of a glue. GlueBoost gets more compliments from its users than any other.

Yeah, in the research I have done into cracking CA Stick Fast has been named as a culprit quite frequently. I actually reached out to the manufacturer via email, and the Stick Fast Thin that we've been using is not flexible at all once cured so is clearly not ideal for material that is likely to change dimension due to temperature or humidity fluctuations.

 

[JohnU]

Ive also had that issue with Stick fast, especially when using the accelerator. I now use Gluboost finish. They have both CA (red and green labels) and CA Finish formulas (orange and blue labels). Their finish was made for applying to and fixing guitar finishes. They are formulated to be used with their accelerator to get the proper cure and layering and I've never had an issue with any of them. It's all I use now over wood and acrylics for a great finish, and it's much quicker to get the results.