I glued up some red cedar stock using Pl premium. Wood was between 12-14% moisture content except one piece that was close to 20%.
Glued up 5 pieces of 20″ long 4 x 4, edge surface of 3 1/2″ was coated with glue.
Wood was weathered gray from being stored outside , I very lightly sanded it to remove any dirt etc., wiped the dust off then glued and clamped it for 24 hrs.
Today I went to work the glued stock and one piece broke off right at the glue line. It appears the glue adhered to the weathered “grey/silver” wood fibers but did not penetrate beyond that and the wood itself failed in a paper thin strip across a 3 1/2″ glue line.
I was using a mallet and chisel on the stock at the time but not on the piece that broke off.
Any input on the reason for failure?
Replies
wrong glue.
Jeff
Buck Construction
Artistry In Carpentry
Pittsburgh Pa
Pl Premium is supposedly OK for cedar, why the wrong glue ?
"Poor is not the person who has too little, but the person who craves more."...Seneca
"why the wrong glue ?"glues work in different ways. Some are a chemical bond, some are mechanical, and some are simple suction.PL Premium is a polyurethen glue that employs a measure of all three, but does so with addition of fillers because it is a structrual construction adhesive uised for uneven materials like concrete and floor joists to subfloor.For your joint, you want full contact rahter than to separate the pieces with this layer of filler.
Gorilla glue is a polyurethene glue also, without the fillers. It has more expansion agents in it so it pushes out and into wood poers as it cures. Moisture is the catalyst that causes the curing process with polyurethene glues so the moisture in the wood increaases the chemical bond. If you use Gorilla on wood that is too dry, it actually helps to mist it or to wipe with adamp rage prior to assembly.The older glue was hide glue which works mostly by suction type action, filling pores with gummyness and turning each pore into a tiny suction cup sealed at the edges with high viscosity material. To use it for a joint like this, you needed nearly perfectly mating surfaces to get the pores in contact and aliognment with each other.For your purpose, I would use an epoxy since it will be the most resistant to the water and the strees that water will cause, moving wood fibres.
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Excellent! I couldn't have said it better.Parolee # 40835
I have used Gorilla on WRC outdoors in difficult conditions and it's performed perfectly, although admittedly I put in a lot of biscuits. I've had epoxy failures with redwood--something to do with the tannins--and switched to resorcinol. Don't know if cedar might have the same issues but if I wanted to use epoxy with cedar I would talk to Smith & Co. and see what they recommend. I've had immediate failures with cedar and Tite III, which their chemist said would only work if the wood was below 6%.
The weathered wood is like a thin layer of dry-rot. As you found out it's not very strong and will strip off. Think about it, if you can scratch something off with a fingernail, why should paint or glue add any strength? A glue joint can never be stronger than the substrate material.
Thats is what I am thinking, I probably will have to break all the joints and sand or surface plane down to fresh wood. Not a big deal , all the project is about is a small wooden bird bath bowl and I was using scrap from old jobs up . Once it is in place it will not have mechanical stress or loads placed on it.
"Poor is not the person who has too little, but the person who craves more."...Seneca
Two things stand right out.
I would use a Gorilla glue or Titebond for that sort of joint. The pl has too much body and fillers that would separate the pieces from good contact.
The other, that you make quite obvious is that you need to be down to the real wood when you glue up.
The greyed surface is where UV rays have turned the wood cells into a disintegrating flakey material. Microscopicly, it is not full complete wood cells that you adhered to, but the remnants of such. The greyed wood on that minute level is more similar to old leaves, dry and crumbling. They are there, but no longer a part of the solid chunk of wood.
A more liquid glue might have penetrated deeper and grabbed onto the deeper wood cells for a better glue-up, but planning or sanding deeper is primary, then the type of glue is wrong for this type of joint
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Taunton University of Knowledge FHB Campus at Breaktime.
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>> The greyed surface is where UV rays have turned the... cells into a disintegrating flakey material.Hey, now. Take a good look in the mirror when you say that! Some of us resemble that remark. ; )
"Doubt is not a pleasant condition, but certainty is absurd."
~ Voltaire
hasbeen,
I agree, personally find it rather attractive about myself.;-)
"Poor is not the person who has too little, but the person who craves more."...Seneca
It's not gray, it's DISTINCTION!
"Doubt is not a pleasant condition, but certainty is absurd."
~ Voltaire
Definitely should have planed down the mating edges..the grayed wood was a no-go from the beginning. Piffin's right about the PL premium in this case..I've glued up plenty of cedar for exterior uses w/ liquid polyurethane glue (like Gorilla glue) with excellent results. Epoxy would be best, but probably not necessary if this isn't a structural assembly.
PL Premium WHAT?
Construction Adhesive OR wOOD GLUE?
http://www.stickwithpl.com/Products/detail.asp?PLProductID=14
http://www.stickwithpl.com/Products.aspx?ID=0c90059f-3484-4981-bf6d-c0a67e878bf9
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Thanks All,
Especially Piffin for the education. I used PL Premium Construction adhesive. I had gorilla glue sitting on the shelf, and have used it in the past so I will knock it apart and clean the mating surfaces.
"Poor is not the person who has too little, but the person who craves more."...Seneca
Jeff Buck hit the bullseye, and Piffin added more arrows on top. When you clean up the cedar, mill it until an observer cannot tell that the wood has ever been out in the weather. If it looks funny to you, it looks funny to the glue. Jointing and planing will be faster and better than sanding, although a lightly sanded surface is better to bond to if using epoxy.Bill
Thanks Bill. I didn't realize that they had a wood glue too. Have you used it? Probably about the same as Gorilla.
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I'm not Bill, but the PL liquid poly glue (not just for wood ) is good stuff, just like their other products.
I've tried them all that I've come across, always like to experiment and find a better tool/or product. With that said, one that I would stay away from is the one made by Titebond (black and purple bottle). Excessive foaming and I can often break the joint at the glue line.
NoI have not used it either.Used to get some Elmers (or was it Tigtbond) poly that I like better than Gorrila. And cheaper too.But all I see around now days is Gorrilla..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
I don't know which brand it was, but I did use another than Gorilla once. It wass way too thick, but I think it was because there is a shelf life on the stuff and Gorilla outsells everything else, so it had been there too long.
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I've used Gorilla Glue, the Elmer's stuff and the PL polyurethanes. I think shelf life may have something to do with it, but the PL stuff seemed to be super think and in general, a pain to work with. Usually I'll buy the Elmer's due to the cost.Wood Magazine had a glue test in the Sept 2004 issue that rated Gorilla glue the top spot of the Polyurethanes tested (Titebond and Elmers were the others. PL doesn't seem to make up much of the market). Gorilla Glue tied for the strongest bond with Elmers.
Elmers sounds interesting then
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I like the elmer's "ultimate wood glue" better than gorilla. It's a bit thinner, easier to get out of the bottle. Seems to work the same.
Also, the dumb little cap on gorilla glue bottles is tiny and white- tough to get off without pliers half the time, and easy to lose if you're not paying close attention.zak
"When we build, let us think that we build forever. Let it not be for present delight nor for present use alone." --John Ruskin
"so it goes"