glue 1 surface or 2

[Richard Hutchings]

After reading Stephens post where he mentioned gluing both faces of the laminated legs, it got me thinking. I generally avoid that and feel gluing one surface is plenty. I think if I was gluing up a mallet, I might go that extra mile but I'm more of a glue one surface guy. Prove me wrong and I'll change my wicked ways.

[Charles Taylor]

Applying glue to both surfaces is the example I followed when beginning woodworking. I still usually do it that way more than 20 years later, at least when using PVA glue.

That said, I did a glue up your way yesterday evening, and I expect it'll be fine, especially since the workpiece spent the night under good clamp pressure.

[Luke Dupont]

I think at the end of the day, the amount of glue is what is important, right?

I just try to use "enough" glue, but not "too much," because "too much" is a huge mess. I usually just put glue on one surface, except when I don't, which is mostly up to intuition and how I feel about how much glue is necessary or not for two given pieces to join up...

I'm a lot more generous with things like mortises, or anywhere that endgrain is present, while I'm much more conservative with flat, well prepared faces.

And when I can I don't use glue. I mean, some things just don't need gluing, but we like to glue them anyway. Sometimes it's better not to glue things when considering wood movement or future modifications and repairs. I can't tell you how many times I've wanted to change or fix something that was glued...

But, I only think I know what I'm doing. I've learned enough to know how little I know, so don't put much stock in anything I say or do! Listen to much smarter and more experienced people instead.

[Kevin Jenness]

As long as you get enough glue on to saturate both faces plus a minimal amount of squeeze-out gluing one face is fine. The spread rate needs to be heavier than when coating both faces. Double coating ensures no holidays. I definitely glue both faces of mortise and tenon joints as the sliding assembly can prevent full glue transfer from only one surface.

[Jim Koepke]

It could be that both are right. (with PVA glue)

If there is enough glue to squeeze out, then applying glue to only one side may have the same effect of glue being applied to both sides of a joint.

If applying a thin coat of glue to the surfaces it might be better to give a thin coat to both (all) sides of a joint.

My understanding may be incorrect. This being PVA glue absorbs in to the wood along the joint. When it dries the molecular structure of the dried glue is holding the pieces together as long as there isn't a gap.

PVA glues are not a gap filling adhesive. Some epoxy glues can be used to bond across gaps.

jtk

[lou Brava]

Many many years ago an old guy who I was working for told me to spread glue on both surfaces & called it "sizing" the joint ? Never questioned it and continued to "size" every thing I've glued up for last 40 years. Maybe unnecessary but never had a failure just probably wasted a lot glue :D

[Luke Dupont]

It could be that both are right. (with PVA glue)

If there is enough glue to squeeze out, then applying glue to only one side may have the same effect of glue being applied to both sides of a joint.

If applying a thin coat of glue to the surfaces it might be better to give a thin coat to both (all) sides of a joint.

My understanding may be incorrect. This being PVA glue absorbs in to the wood along the joint. When it dries the molecular structure of the dried glue is holding the pieces together as long as there isn't a gap.

PVA glues are not a gap filling adhesive. Some epoxy glues can be used to bond across gaps.

jtk


Would you do anything differently with hide glue?

[Prashun Patel]

I've done it both ways. It doesn't matter in my experience.
I pay way more attention to the flatness.

In fact, there is an argument to be made that doing one surface only, then smooooshing the two surfaces together and witnessing how well the transfer coverage is on the other piece is evidence that your two surfaces are properly mating.

[Mike Henderson]

I was taught to put glue on both surfaces but that always gave me too much squeeze out. A few years ago, I switched to glue on one surface only. Never had any problems with that approach. It saves a small amount of time - the time you'd spend putting glue on the other surface.

Mike

[Richard Hutchings]

I always do that.

[James Pallas]

I only glue both sides when gluing end grain. On the end grain piece I put glue on and rub it in good with my finger. I than glue the other piece and go back to the end grain piece and put a little more on before making the joint up. Doing the end grain this way was what I learned as sizing. Try it for yourself. Put some glue on end grain spread it, let it sit a minute or so and look again. It will look dry especially on open pore stuff like oak.
Jim

[Edward Weber]

As long as you get enough glue on to saturate both faces plus a minimal amount of squeeze-out gluing one face is fine. The spread rate needs to be heavier than when coating both faces. Double coating ensures no holidays. I definitely glue both faces of mortise and tenon joints as the sliding assembly can prevent full glue transfer from only one surface.


+1
I apply glue (PVA) to both mating surfaces. I prefer to see the glue evenly applied, rather than assuming that full coverage was obtained simply by judging the amount of squeeze out.
End grain joints can require more glue or a sizing coat to properly adhere, due to the nature of the wood.
I sometimes think, applying a light coating of glue to both sides rather than a heavy coat on one side uses less glue in the long run. That's just a WAG

[steven c newman]

I was doing a lamination on those legs, and used a roller to moosh the beads out...

M&T joints: Coat the tenon.

Gluing up a flat panel, like for a table's top....one bead down one edge...then "rub" the 2 parts together, until I feel it begin to stick..

Dovetail Joints: I brush on glue to the half that is sliding into the joint...but not the other half...

[Jim Koepke]

Would you do anything differently with hide glue?

Not having ever used hide glue my answer to this could be meaningless.

Though isn't that how a rubbed joint is put together?

jtk

[John K Jordan]

After reading Stephens post where he mentioned gluing both faces of the laminated legs, it got me thinking. I generally avoid that and feel gluing one surface is plenty. I think if I was gluing up a mallet, I might go that extra mile but I'm more of a glue one surface guy. Prove me wrong and I'll change my wicked ways.

What kind of glue? What does the mfgr recommend.

I recently used System Three T88 epoxy when edge-joining 1” bubinga/guatambu/walnut. The instructions were clear to apply epoxy to both surfaces and don’t over-clamp.

The actual effectiveness of the joint with glue on one or both surfaces might depend on the wood species and surface prep.

You could test this. Prepare a number of pairs of test pieces, perhaps 4/4 about 2x2 or so, prep the edges and glue/clamp with both methods. I’d prob make at least 4 or 5 tests for each method. After an appropriate amt of time hold one half in a vice and smack the other with a hammer or apply some other force. (I might use a big wrench for a non-impact force.) See if one method holds better. For a more complete test repeat with other species, perhaps combinations.

[Richard Hutchings]

Yeah but somebody must have done these test already I would think. I'm talking strictly Titebond original. Never read the label, maybe I should start there.

[mike stenson]

Would you do anything differently with hide glue?
Liquid or hot hide glue?

Liquid I'm generally a one side kind of guy. Except I'll size end grain. If I'm getting squeeze out, there's enough glue IME. I rarely use hot hide glue, and it's been a long time now so I'm not going to comment on it.

[Richard Hutchings]

Hide glue is a whole nuther can of worms.

[mike stenson]

Yea, but it's just so convenient it's about all I use anymore.

[James Pallas]

I like hot hide glue and would use it more. I use it when doing a lot of gluing. Since I do mostly small work now its too time consuming. Its great for rub joints cleans up easier and does a good job if not expected to be water resistant. I do rub joints with PVA also. It works about the same but seems a little more delicate for a few minutes longer. I tried liquid hide but don’t use enough. The small bottles never seem to be enough and the big bottles go bad even in the fridge before I can use it. Works fine.
Jim

[Richard Hutchings]

Convenient?? No, it's a PIA. Warming up the glue and warming the parts or the whole shop is not convenient to me. I've used quite a bit of it and finally said, enough of this foolishness. Squirt some glue and be done, that's my new motto.

[mike stenson]

I see you missed where I said I don't use hot hide glue often. But use liquid. Which offers all the convenience of PVA, with all the convenience of hot hide glue..

[Michael Schuch]

For me it depends on the particular wood, the particular joint, the type of glue and how much stress the joint will be under. For a joint that will be under a lot of strain I will apply glue to both pieces.

I have also found that in many glue-ups the two pieces might not go together immediately, they might stand for a bit while the other pieces have glue applied to them and be assembled. If a mating pair might stand open for a while I will usually coat both sides so they both have a chance to penetrate the wood surface while they are sitting.

When I do apply glue to both sides I usually apply a thinner coat of glue to both sides and less overall glue which results in less squeeze out and less clean up.

[John K Jordan]

Yeah but somebody must have done these test already I would think. I'm talking strictly Titebond original. Never read the label, maybe I should start there.

The scientist/engineer in me often suggests I try things myself. Before I glued up my latest projects I did that test with the T88 epoxy and samples of the exact wood species. It gave me confidence my project
would stay together.

Maybe try asking Sir Google. You'll find recommendations, some perhaps from sources you trust. Google even told me Titebond makes it easy to ask application questions: http://www.titebond.com/contact

But if you do it yourself with your wood, surfacing, exact type of glue, amount of glue you apply, working time, and typical clamping pressure then you'll know and it might help others.

[Tom Bender]

Usually both surfaces because it means more glue in the joint with less chance of it running out.

However for M&T it is often better to apply to the mortice only, because glue applied to the tenon can be scraped off when sliding together and make a mess.

[Mike Henderson]

Convenient?? No, it's a PIA. Warming up the glue and warming the parts or the whole shop is not convenient to me. I've used quite a bit of it and finally said, enough of this foolishness. Squirt some glue and be done, that's my new motto.

I agree with that regarding hot hide glue. For any glue up of size, it's very difficult to keep the glue liquid long enough to get the parts together. I can't imagine how our ancestors glued up dovetails with hot hide glue. They must have put a lot of urea into the glue. Or maybe the dovetails were mechanically strong enough that it didn't matter about the glue.

I can easily see why the woodworking industry quickly went to modern glues.

Mike

[Warren Mickley]

I was taught to use hot hide in 1966. I have glued hundreds of blanket chests, carcases etc, and thousands of drawers. Also thousands of mortise and tenon joints. It helps to have experience. I have never used an additive; it is not necessary or desirable.

I usually glue both surfaces.

[Andrew Hughes]

I wet both surfaces when I’m gluing up. The one exception is gorilla glue the stuff that foams.
My reasoning is partly superstition and I discovered poor gluing practice in reclaimed furniture or restoration work. I’ve easily taken apart furniture with just a wiggly line of glue and dowels that hardly had a drop.
I shouldn’t complain because it makes my job easier.
If my work where to survive long enough for a restoration someone’s not going to be happy. :)

[Mel Fulks]

Hot hide glue for veneering was thin . Stop the vicious cycle of too viscous glue.

[Richard Hutchings]

Warren, I think you are far beyond a hobbyist. Woodworking day in and day out to make that many glue joints certainly allows for having a glue pot at the ready. I spend 1/2 hour to an hour in my shop and then I'm off to my job or whatever. I think even in retirement I won't be spending that much time Woodworking. Maybe I'll jump to a couple of hour here and there throughout the day so it still won't make a lot of sense for me. At least that's my thoughts right now, not having a crystal ball. Don't get me wrong I do enjoy using it when I have more time but that's rare these days. Give me some Titebond.

[chris carter]

I tend to do both surfaces because better safe than sorry. Also, by doing both surfaces I can apply thinner amounts and I find it’s less messy in terms of application.

I mostly use hot hide glue. If I need more time for a complicated glue-up then I just add salt which works phenomenally well and takes all the (brain) stress out. As a woodworking when I have a spare moment kind of guy I cook up my glue in a large batch and then pour it into silicone ice cube trays and freeze it. Then I pop those into a container and store the cubes in the freezer. When I know I will glue something up I just have to grab the appropriate amount and put them in the pot (glass spice jar in a baby bottle warmer) 15 minutes before I need the glue. Whatever glue is left over stays in the jar and goes in the fridge. If I don’t know that I’ll need glue in the next couple weeks then I just pour it into an ice cube tray and re-freeze it and put it back with the others in the freezer. I used to keep a bottle of LHG around for convenience, but when my last bottle got old I just didn’t buy it anymore as I just was rarely using it. The ice cube thing has been convenient enough for me.

I think they didn’t figure out that you could extend the open time of hide glue with urea or salt until the middle of the 19th century. Before that if you had more glue to apply than was humanly possible in the short amount of time available you had to heat up the wood parts and/or the entire shop. To me that sounds like a gigantic pain the butt (and expensive trying to heat the whole place up).

[Warren Mickley]

Warren, I think you are far beyond a hobbyist. Woodworking day in and day out to make that many glue joints certainly allows for having a glue pot at the ready. I spend 1/2 hour to an hour in my shop and then I'm off to my job or whatever. I think even in retirement I won't be spending that much time Woodworking. Maybe I'll jump to a couple of hour here and there throughout the day so it still won't make a lot of sense for me. At least that's my thoughts right now, not having a crystal ball. Don't get me wrong I do enjoy using it when I have more time but that's rare these days. Give me some Titebond.

I was responding to this quote in the previous post:

For any glue up of size, it's very difficult to keep the glue liquid long enough to get the parts together. I can't imagine how our ancestors glued up dovetails with hot hide glue. They must have put a lot of urea into the glue. Or maybe the dovetails were mechanically strong enough that t didn't matter about the glue.

Or maybe they had more experience using hide glue.

Additives in hide glue to slow down evaporation also make it make it vulnerable to gain moisture and get gummy when the humidity is high, making for weak joinery. Yellow glue and white glue make the joint much more difficult to disassemble for repair. Nobody wants to restore stuff like that, so more likely to be thrown away.

As Andrew Hughes said yesterday:

If my work were to survive long enough for a restoration someone's not going to be happy.

[Luke Dupont]

I was responding to this quote in the previous post:

For any glue up of size, it's very difficult to keep the glue liquid long enough to get the parts together. I can't imagine how our ancestors glued up dovetails with hot hide glue. They must have put a lot of urea into the glue. Or maybe the dovetails were mechanically strong enough that t didn't matter about the glue.

Or maybe they had more experience using hide glue.

Additives in hide glue to slow down evaporation also make it make it vulnerable to gain moisture and get gummy when the humidity is high, making for weak joinery. Yellow glue and white glue make the joint much more difficult to disassemble for repair. Nobody wants to restore stuff like that, so more likely to be thrown away.

As Andrew Hughes said yesterday:

If my work were to survive long enough for a restoration someone's not going to be happy.


I've always wanted to learn to use hot hide glue and intend to give it a try at some point. I like liquid hide glue and tend to use it, but I'd like to try the "real stuff" at some point, both to find out if there's any advantage, and as a learning experience.

What's your advice on how to use it well and how do you address common problems such as gluing up large / complex pieces?

[Richard Hutchings]

Of course the thread transformed into a HHG thread. That's fine with me, maybe I'll learn something and want to fire up the pot again. I already know in my heart that HHG is the best woodworking glue on the planet, no denying. I haven't tried the Frank Ford ice cube tray thing yet and maybe I should. I think this is where Chris may have got the idea, I could be wrong but Frank did a lot of testing on HHG and had some great ideas.

He tested it's resistance to heat and found that a fully cured HHG joint was just about impossible to separate using heat alone. Steam is really the only way to separate them and it works really well for guitar dovetails.

Those cubes of HHG can be microwaved for quick use, I never tried it but again I should because I really love the properties of HHG.

I have in the past removed backs from a guitar and mandolin and reglued them with HHG using technique where the glue is applied to both surfaces and you take as much time as you want, let it cure a little. Set the back on the instrument and clamp it up and just go around the seam with a heat gun, violin makers used an oil lamp, and the fresh glue would start melting and the joint would close up solid.

I think I'm talking myself back into HHG, damn!

[steven c newman]

Have never used any form of Hide Glue....and I doubt IF I ever will.....kind of set in me ways...I guess.

478809
Coated the tenons completely, thin coat... no glue IN the mortises, no room....almost no squeeze out. Bottle of glue has the face of a Gorilla on it....

My shop, my rules?

[Richard Hutchings]

And there's no reason to start. Keep on doing what you do.

[Jim Koepke]

And there's no reason to start. Keep on doing what you do.

As the saying goes, "you can't teach an old dog a new trick," unless the old dog wants to learn a new trick.

jtk

[John K Jordan]

Have never used any form of Hide Glue....and I doubt IF I ever will.....kind of set in me ways...I guess.

…

I was convinced by an expert and a book of the importance of using hot hide glue for one project: rebuilding a player piano. Rebuilding requires disassembling many parts, wood-to-wood, wood-to-bellows cloth. Some parts can be taken apart cleanly by applying heat with an old clothes iron. The idea of sticking with hide glue is to be kind to the guy who rebuilds it the next time, maybe 50 years later.

I haven’t used it for anything else.

JKJ

[Andrew Hughes]

In my area I idea of heirloom furniture isn’t something people think about.
I see society more into temporary furnishings.
Ive made a couple pieces that can be easily taken apart and put back together. Wedged tenons and doweled joints.
I like using old brown glue for small boxes but it mostly for my own personal reasons.
Good Luck everyone

[William Fretwell]

The only way you can have one rule, is to coat both surfaces.

Getting past that, if your face joint touches over say 60% of a large area it will be very strong so the coating is a non issue if done in a timely fashion. Adding glue to the other surface will not increase contact area.

If your glue up is delayed and the one surface with glue dries too much it may well not transfer to the other surface well and give a ‘dry joint’. Woods with high absorption will speed drying and if there is high absorption then thinly coating both surfaces with partial drying ensures a better joint with far less squeeze out; such as edge glueing white cedar.

Joints with modest area, subject to mechanical stress, such as mortice and tenon should be well designed and made with appropriate shoulders and pegged inside such that no glue is required. Then the addition of glue to the tenon and back of the mortice is just a nicety.

Dovetail joints in drawers, carcasses etc have a large surface area and are usually very sound mechanically when assembled, so modest glue on one surface lessens clean up and finish application issues in a highly visible joint.

The worst case relying on glue is edge jointing boards. The contact area of the joint is key. Does thin application to both surfaces generate less squeeze out? Does one sided application provide enough glue? Yes there will be enough glue, will there be enough contact area?

[Mike Henderson]

I would suggest a test, which I have done. Put glue on one surface, then clamp the boards together. Do a good clamp, just the same as you would do normally. Then take the boards apart and see if there is glue on the surface that was dry.

In my tests, the "dry" surface was fully coated. Clamping causes the glue to be spread well over the surface. Of course, you can't starve the first side with glue - just apply the normal amount of glue.

Mike

[Kevin Jenness]

Joints with modest area, subject to mechanical stress, such as mortice and tenon should be well designed and made with appropriate shoulders and pegged inside such that no glue is required. Then the addition of glue to the tenon and back of the mortice is just a nicety.

There are many designs using mortise and tenon and spline joints that don't lend themselves to pegging and do require a thoroughly glued surface for optimum strength. Do an experiment: Put together a well-fitted mortise and tenon, a Domino joint and a biscuit joint with glue on only one side of the joint, take them apart and check out the glue coverage on the unglued side, then decide how to proceed.

[mike calabrese]

Both sides for many reasons which are just my reasons and beliefs.....no scientific data attempted or suggested here, like someone said above here my shop my way.

Glue penetrates into wood coating one side provides more glue penetration there and none in the mating piece until joined together.

Depending on elapsed time and climate considerations PVA glue tens to skin over rather quickly. This may reduce the transfer of glue to the dry side joint and lessen the glue penetration.

PVA before cure will always bond to PVA totally

End grain joints are prone to absorbing glue quite rapidly reducing the surface coating available for bonding and then sharing the available coating with the dry side joint can lead to a glue weak , glue scarce joint.

It is more beneficial to manage the amount and method of adding glue to a joint. A reasonable full coverage to both sides insures the entire joint has access to the stuff that will keep the joint together for years. Why take the chance, slim as it may be that there may be a relative dry or weak glue transfer with a wet to dry joint.

A gallon of glue is or was 4 times more expensive than gas for your car but a gallon of glue will take you way farther than a gallon of gas in your car why sweat the economics.
mike calabrese

[William Fretwell]

I have a 90 degree joint in 3/8” Baltic Birch plywood with one #10 biscuit (the smallest). I offer it to clients to see if they can pull it apart, they can not.

[Alex Zeller]

I glue both sides as I like to work the PVA into the wood. The exception is if I can move both pieces around some to help spread the glue. If something works why change. I just don't want a glue joint to fail down the road when it'll be hard to fix just because I wanted to save a little time and glue.

[James Pallas]

Most of the glue joint failures I have seen are not due to glue failure. A joint usually fails because of stresses beyond the capability of the glue, gap filling, wood shrinking, cross graining, wrong glue used, over stress, and abuse. It doesn’t mater if you spread it with your finger or opposing pieces as long as both sides are coated.
Jim

[mike stenson]

Most of the glue joint failures I have seen are not due to glue failure. A joint usually fails because of stresses beyond the capability of the glue, gap filling, wood shrinking, cross graining, wrong glue used, over stress, and abuse. It doesn’t mater if you spread it with your finger or opposing pieces as long as both sides are coated.
Jim

I wish we had a like button sometimes.

[Mike Henderson]

This is one of those situations that lend itself to testing, rather than opinion. My suggestions:

1. Spread glue on only one surface, clamp it to another board, then take the glue joint apart and see whether the "dry" surface is fully coated.

2. Glue up two samples, one with glue on one surface and one with glue on two surfaces. Let the glue cure well and then try to break the pieces apart.

3. For those worried about the glue developing a "skin". Put glue on one surface and let the glue sit for your selected time. Then perform the first two tests. Report how long you let the glue sit on one surface.

Report your results here. I've done the first two tests - I never worried about the glue developing a "skin" - and I'm very satisfied that applying glue to only one surface is quite adequate.

Mike

[Scott Winners]

Plenty of observations here. My baseline is to put glue on one surface, wiggle the mating surfaces against each other, then clamp.

My benchtop, 2x4 Doug Fir, was glued face to face for a top 3.5 inches thick 3+ years ago with this method. I then brought in some 8x8 and some 4x10 to learn barn sized joinery on because my eye sight isn't what it used to be. I have used my bench top like rented mule, no hiccoughs. I upgraded to the one inch Crucible holdfasts, use a 6 pound engineers hammer to set those, and a 1.5 inch Barr chisel to cut and pare mortises. I have clobbered the Barr chisel with the six pound hammer more often than I care to admit.

I edge glued a small table top with the same method, nominal 11x32x4/4 poplar in two inch wide strips, same regimen. It was in service for two years before I had a different problem with the total assembly. I have not been able to break my glue joints over the winter using an inside hammer and inside methods. Local we got another inch of snow here Monday morning, but in a few days or weeks I will take the poplar top outdoors with an outside hammer and see what breaks first.

For stuff I can't wiggle, like apron tenons going into the mortises in table legs, I apply glue to both surfaces before assembly. If you can wiggle the mating surfaces 3-4 inches and get relatively even glue squeeze out, I don't see problem applying glue to only one surface.

[John Kananis]

When using pva, I either glue both sides or just the one side, then rub the joint faces, pull them apart to see that glue has spread evenly on both mating surfaces and then clamp together.

For hide glue, I glue both surfaces always. My wife laughs whenever she comes into the shop while I'm using hide glue. I stole a little fondue pot of hers many years ago and still use it to keep my squeeze-bottle off glue warm. Best thing ever really, keep it on low and you have all the time on the planet to glue stuff up.