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Exterior Glue Failure - Part One!10/3
About 3 years ago, we started having problems with exterior door panels opening up at the joints when we glued for width. We were using TiteBond III, thinking it the best for our application.
After repairing/replacing about 12-14 door panels, and $14,000 worth of effort, we probed a little deeper after we cleaned the shop of any TBIII.
We learned from the techs at Titebond that TBIII looses strength as temperatures increase. At 180F degrees, the glue looses about 60% of its strength. Go to 190F degrees, and it is about 80% of its strength. The glue does not regain its strength as the temperatures return to a more normal range.
The panel photos below typify what we found when we removed them from a door. These are flat panels, 1-1/2" thick, two plies for thickness, with epoxy sealed end grain. I admit it was hard to believe.
The first photo shows a white line in the black field that is the indicator of a failed joint. Just open a slight bit.
The second photo shows a cut out part of the panel. It is two ply in thickness, with the joint to the exterior the top. It is failed, with glue residue in an orange color. The wood broke in the second plies' thickness, showing the split, lighter color wood. This indicates the glue failed halfway thru the panel - 7/8" at this point.
The last photo shows the joint where the glue failed and where it held. The inside of the door was much cooler, and the heat from the exterior hot face penetrated about three quarters of the way thru the panel - all except for that last bit on the lower edge.
The problem panels were all dark. All faced East, with just one or two facing West. They were all Honduras Mahogany. They were made over the period of 2 years.
I've never been a big fan of TB3. I've found it too expensive and with no benefit over TB2 other than it is water "proof" instead of water "resistant"......i.e. submersible. I've never felt a need for anything I've made to be that waterproof.
I feel for you in this situation. I had some curved base fail once because of a delaminated bending ply backer. It was a poor choice on my part but I was trying to save the customer some money using the ply backer instead of solid wood.
Neither the plywood distributor nor manufacturer would discuss the matter with me. In the end I turned to my liability insurance company for coverage on the repair. They were very good about it and covered the loss. It was the only time in 30+ years that I turned to insurance for any sort of business problem.
Sorry to hear the extent of your TB3 whoas. You've alluded to the failure over the last year. This is the first time I've read the specifics.
I bought one of the small bottles of TB3 when it first came out. I didn't like it from the start. We didn't even finish the bottle. Gorilla Glue left the shop after one year of little use.
TB1 & epoxy(MAS, West System) only in our shop. TB1 is one of the few glues I've ever used that doesn't telegraph thru a really good paint job. Epoxy is the ideal waterproof wood glue. More expensive. More wasteful. Mixing takes seconds. At the end of the day the epoxy won't fail. However, we may fail in our construction method.
I had the exact problem with a door using the same glue.
I've had the same problem with the veneer seams on the bottom rail of two doors. I glued the veneer seams with TB III and then glued those panels to the stave core with Plastic Resin Glue. These were wide rails at around 12" so each veneer was around 6" wide. Within a year both split right at the veneer seam. They didn't bat wing open proving the PRG was still holding each piece to the stave core; they just opened up at the seam like shown in your first photo. On one door I replaced the bottom rail. On the other I forced some finish into the split to hopefully preserve the integrity of the finish, and we're just watching to see what happens.
While back here i posted about a set of cabinet doors that a customer picked up and left inside his truck with the windows up in the sun for over half a day even after i specifically told them to not let them sit in the heat. All the panel joints opened at the ends. This was with Titebond Original so i know Original loses its strength when exposed to excess heat too.
TB 1 is a heat responsive adhesive. You can use it as a veneer contact cement by applying it to both surfaces, letting the glue dry, putting the pieces face to face and then heating the glue with an iron. The glue will soften under the heat and the two surfaces will bond. This is partially why it is a poor choice for the Workrite wood welder which in effect heats the glue to cure the joint. TB2 on the other hand hardens with heat which is why it works so well with the Workrite.
We had a similar issue as the doors left in the car with TBIII. We cnc'd some plaques for a wholesale customer that were painted black on blanks laid up using hard maple with TBIII. They have a retail shop and we have repeatedly made it clear that putting them in their store front glass display case in direct sun was a guaranteed failure. One of the owners picked up the plaques and left them in the front seat, windows up, on a 90+ day in the full sun. Every glue joint failed and opened for inches on the ends. We spring joint hard maple almost daily and have never had a failure.
We credited the job and replaced with the customer after they somewhat insinuated it must have been a manufacturing issue.
When we replaced them we laid up three more identically and put them on the front seat of my car in the sun on a similar day and within 4 hours they failed identically.
We very rarely need water proof glue. As it happens I'm about to start on a porch rail & balusters for my own house. I used to always use resorcinol phenol formaldehyde for exterior work. Totally water proof, expensive. About $130 a gallon! So I was considering TB3. Thanks guys, you talked me out of TB3. Porch project will be Cypress.