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Sizing Glue

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Forum topic by richgreer posted 08-22-2010 11:06 PM 2561 views 0 times favorited 14 replies Add to Favorites Watch
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richgreer

4541 posts in 2541 days


08-22-2010 11:06 PM

I was watching the WoodSmith Show on PBS yesterday. They were gluing up some mitered corners with no biscuits or splines. They talked about a technique that involved “sizing glue”. It went as follows – -

Place a small amount of glue on both gluing surfaces, spread it out and let it dry for 2 -3 hours. They refer to this glue as “sizing glue”. Then apply a small amount of glue to one surface and clamp it up.

I admit, I have never heard of this before. Can anyone comment on the advantages (or disadvantages) of this technique versus just gluing and clamping?

Note – they used the same glue (Titebond III) in each step.

-- Rich, Cedar Rapids, IA - I'm a woodworker. I don't create beauty, I reveal it.


14 replies so far

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uffitze

199 posts in 2422 days


#1 posted 08-22-2010 11:27 PM

because a miter is basically gluing end grain to end grain, sizing stops the wood from “sucking” the glue away from the joint.

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Tony_S

607 posts in 2550 days


#2 posted 08-22-2010 11:32 PM

‘Sizing glue’(typically) is nothing more than a ‘prime coat’ of glue to seal a porous surface to avoid a dry joint.
Done quite often with MDF….especially MDF Mouldings (Miters).

-- It is the mark of an educated mind to be able to entertain a thought without accepting it. Aristotle

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Tony_S

607 posts in 2550 days


#3 posted 08-22-2010 11:54 PM

2 to 3 hours seems a bit excessive to me….if I were to do it myself (not often) I would typically only wait 10 or 15 Mins myself. Just long enough for the ‘sizing’ coat to start to set up.

-- It is the mark of an educated mind to be able to entertain a thought without accepting it. Aristotle

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Gregn

1642 posts in 2450 days


#4 posted 08-23-2010 12:10 AM

I have heard of this before, but always wondered if it actually made the glue joint stronger?

-- I don't make mistakes, I have great learning lessons, Greg

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docholladay

1287 posts in 2525 days


#5 posted 08-23-2010 12:41 AM

I haven’t ever used the technique – at least not intentionally. I have had a few miter joints that came loose and had to be reglued. effectively, I had a sized joint then. From what I have read about glue size, usually the glue for the size coat is thinned in half with water. I never really thought of using it with MDF, but it sure makes sense to do it the way that stuff soaks up the glue. Also, as others above have mentioned, 2-3 hours would have the size coat completely dry. That could potentially lead to a need to sand the joint because of lump or something like that from dried glue. In 10-15 minutes, you could probably avoid that.

-- Hey, woodworking ain't brain surgery. Just do something and keep trying till you get it. Doc

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a1Jim

115206 posts in 3044 days


#6 posted 08-23-2010 02:26 AM

Sizing can be used in a number of ways either thinned or not thinned . It’s a pretty common way to treat end grain and some folks do use it as anti blotching technique. for most end grain joinery I still would suggest some sort of real joinery. Depending on what type of joinery your using

-- http://artisticwoodstudio.com Custom furniture

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Canadian Woodworks

702 posts in 2536 days


#7 posted 08-23-2010 04:06 PM

I do this on my chairs, but leave it on for about 10 minutes, scrape it all away ( whatever did not get absorbed ) apply a new thin layer of glue and attach.

I even do this with the rocker leg joints where we use epoxy.

-- Paul Lemiski, Ontario Canada, Custom Wooden Rocking chairs and tables http://www.canadianwoodworks.com

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Jeremy78

11 posts in 414 days


#8 posted 10-22-2015 07:49 PM

1

-- If it's worth doing, it's worth doing right

View jdh122's profile

jdh122

879 posts in 2284 days


#9 posted 10-22-2015 07:54 PM

I’ve done it with plywood or MDF (making shop cabinets) but I’d be really reluctant to let it dry 2-3 hours. Wood glue doesn’t really bond very well to dried wood glue and it seems to me that this is what you’re setting up with that long a dry time.
On the Titebond website they say to let the sizing dry for “no more than two minutes”, which is about how long I’ve usually done it (http://www.titebond.com/application_tips.aspx).

-- Jeremy, in the Acadian forests

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bondogaposis

4036 posts in 1818 days


#10 posted 10-22-2015 08:35 PM

It is to prevent glue starvation which is one of several reason why endgrain joints are weak. 3 hours does seem a bit long, but TB III has a lot longer working time than TB II, I would think that 20-30 minutes would be enough.

-- Bondo Gaposis

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AandCstyle

2575 posts in 1724 days


#11 posted 10-22-2015 09:32 PM

I do it routinely for mitered boxes, sides are 3/8” to 1/2”. I dilute the glue 50% with water and apply it and let it cure for a couple minutes then apply a thin coat of full strength glue. I would never use it for a joint that could accept a spline.

-- Art

View poospleasures's profile

poospleasures

544 posts in 1951 days


#12 posted 10-23-2015 12:26 AM

I us full strength sizing on all miters or anytime end grain must come against long grain. The sizing makes the joint many times stronger than without. Not saying this is like long grain to long grain but for making jewelry boxes and the like the joints are plenty strong. Larger stuff or joints under tension must have some type of spline or pin. Patrice a few good fitting miters with and without sizing and see the difference by breaking them apart.

-- I,ve had amnesia for as long as I can remember. Vernon

View WoodNSawdust's profile

WoodNSawdust

1417 posts in 643 days


#13 posted 10-23-2015 12:33 AM

In the Marc Sommerfeld cabinet making videos he teaches this but usually is only a couple of minutes between the first and second coats of glue. Since then I have used the same technique. I can’t say if it is accomplishing anything but if it works then it is worth it.

-- "I love it when a plan comes together" John "Hannibal" Smith

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bearkatwood

1214 posts in 478 days


#14 posted 10-23-2015 01:01 AM

If you are using a ring porous wood you don’t need sizing as much, because of the tylosis that closes off the end grains the glue can’t escape the joint as bad. Tylosis exists in most all trees as that is basically how they grow upward, but the ring porous woods end grains collapse when drying. The usual sizing of an end grain joint is to thin down the glue to lower the viscosity allowing it to penetrate the wood and basically clog the pores keeping the second application of glue where you want it at the joint. I very seldom use this and prefer to use some kind of mechanical joint to back it up. Take a look at Japanese tea tables that have a three way mitered joint, mostly end grain, traditionally they didn’t use glue at all and instead relied on the mechanics of the joinery to hold it together. Sizing can be used to hold pieces together, but I wouldn’t count on it to last.

-- Brian Noel

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