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Does stain weaken a glue joint?

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Forum topic by richgreer posted 04-22-2011 08:03 PM 15452 views 1 time favorited 21 replies Add to Favorites Watch
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richgreer

4541 posts in 2538 days


04-22-2011 08:03 PM

Sometimes I like to stain individual pieces before assembly. When i do this some of the gluing surface will get stain on it. My theory is that the stain weakens the holding power of the glue very little and maybe none.

If I ever apply a finish before assembly I always make certain not to put finish on a glue surface – but I think it is okay with respect to stain.

Am I right about this?

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


21 replies so far

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docholladay

1287 posts in 2522 days


#1 posted 04-22-2011 08:08 PM

Rich, you pose a very interesting question. I would tend to agree with you on a dye or anything that is nothing more than a pigment/color on the wood. As long as it does not seal the wood to prevent glue from being absorbed into the pores of the wood, I would think your hypothesis (my big word or the day) would be correct. I will be interested to watch this post to see if some more learned individuals chime in with real data vs my guesses.

Doc

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

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docholladay

1287 posts in 2522 days


#2 posted 04-22-2011 08:14 PM

Rich, one thing does come to mind to counteract your idea. Some stains actually have solid particals that make up the pigment in the stain, in those cases, coloration occurs as a result of those solid particals being absorbed into the pores (filling them) of the wood. I can see how this could afffect glue adhesion. Also, it will depend grealy on what type of carrier/solvent that the pigment is dissolved into. Some are in an agent that would partially seal the wood.

Doc

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

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mcase

446 posts in 2592 days


#3 posted 04-22-2011 08:46 PM

Rich,

I pre-stain and pre-finish most of my work. Its ultimately much quicker and you can evenly polish areas that are usually inaccessible. I never allow stain or finish into areas where there will be glue contact. Its not hard to do. IMO any oil based stain would absolutely effect glue adhesion of any water-based glue. I also recommend pre-finishing. Besides the ease of application there is also the great benefit of being able to wipe away all the glue squeeze out with ease. The glue does not adhere to the finish and wipes off cleanly with a damp paper towel. Of course you can glaze and shade the pre-finished piece after assembly for any desired effect.

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Lee Barker

2170 posts in 2314 days


#4 posted 04-22-2011 10:55 PM

We’re guessing until we test it.

From the same piece of wood, glue three (or six) joints: one of clean wood to clean wood, one with half of one surface stained, one with all of one surface stained. (You could do more with, say, dye.)

Clamp and cure.

While that’s going on, devise a way to add incremental, repeatable weight to the joint. There’s a beautiful example of this here.

You will learn not only which joint fails first, but also the degree of adhesion where there is contamination.

You’ll be the first expert on this question, Rich!

-- "...in his brain, which is as dry as the remainder biscuit after a voyage, he hath strange places cramm'd with observation, the which he vents in mangled forms." --Shakespeare, "As You Like It"

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Gregn

1642 posts in 2447 days


#5 posted 04-22-2011 11:40 PM

Here is what I got from Titebond’s web site.
Can surfaces that have been painted or stained be bonded using Titebond Wood Glues?
Most of our glues are designed to bond bare wood. Painting or staining a wood blocks the pores, keeping the glue from penetrating into the wood. The Titebond Polyurethane Glue may work for gluing together painted or stained surfaces, but it is necessary to remember that the overall bond will only be as strong as the bond between the paint and the wood. We recommend that all substrates be clean of any type of paint, stain, or sealer.

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

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richgreer

4541 posts in 2538 days


#6 posted 04-23-2011 12:17 AM

You guys are great. I’m going to change my practices and avoid staining any surface will be a glue surface just to be on the safe side.

As an FYI – - Yesterday I stained the 22 pieces that make up the 2 plant stands that I am making. However, all my joinery will be dowel pin joinery. I did not drill the necessary holes until after the staining was dry. The real important bond here is the dowel inside the holes and that is all bare wood contact.

b.t.w. – For years I have been buying dowel rods and cutting off my own dowel pins. Today, for the first time, I bought some of those pre-made dowel pins (with the fluted sides). The diameter was dead on accurate (not true with some dowel rods) and the fit was perfect. I would almost say that gluing was optional – but I glued them anyway.

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

View Steven H's profile

Steven H

1117 posts in 2523 days


#7 posted 04-23-2011 02:45 AM

Stain and Dyes will not weaken the glue joint, it is the solvents that manufactor put in their products.

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Steven H

1117 posts in 2523 days


#8 posted 04-23-2011 02:52 AM

Let me ask you this

What products are you using?

View a1Jim's profile

a1Jim

115202 posts in 3040 days


#9 posted 04-23-2011 03:07 AM

I say it has to do with what kind of stress is on the glue joint, If you making drawers for small nuts and bolts and pin nail the drawers together ,then I say don’t worry about it, the same with face frames that are pocket screwed together.But if your making cabinets that will hold a lot of weight I always tape of the joint before prefinishing. I view it as a similar situation as when your putting a piece of brown paper in glued up pieces of wood so you can pull it apart later ,think of the finish acting like the brown paper being placed between the two pieces you want to stay together. modern glue is much stronger then wood but finish is not.

-- http://artisticwoodstudio.com Custom furniture

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William

9906 posts in 2306 days


#10 posted 04-23-2011 04:09 AM

Someone above said basically that we’re whistling dixie until it is tested. Well, this exact thought crossed my mind about a year ago and I did test it.
I use minwax oil based stains and sometimes waterbased tinted color stains. I tested both the same way and got the same results from both stains.
I used just a basic butt joint.
I glued six identical joints,
1 gorilla wood glue, no stain
1 titebond, no stain
1 gorilla glue, oil based stain
1 gorilla glue, water based stain
1 titebond, oil based stain
1 titebond, water based stain
I broke all the joint by slinging them on the floor. We are talking simple butt joints on two pieces of wood. They aren’t exactly strong to start with. I let everything cure overnight. Then…...
Both joints with just glue held tight, breaking wood around where the glue joint was was.
All four joints that were stained first broke clean. The glue did not hold like it should. Now, they held good enough that if handled with care, I think the joints probably ould have lasted for year. Under stress though, glue does not hold as well as it was meant to.

-- http://wddsrfinewoodworks.blogspot.com/

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richgreer

4541 posts in 2538 days


#11 posted 04-23-2011 04:14 AM

To respond to Steven H -

The stain in MinWax golden oak. It is their regular stain (not the gel stain).

The glue is Titebond III.

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

View gfadvm's profile

gfadvm

14940 posts in 2153 days


#12 posted 04-23-2011 05:05 AM

Oil based stain [like your MinWax] will absolutely prevent Tightbond from properly bonding.The only glue joints I have had fail were wood stained with oil based stain.The type of wood doesnt seem to matter.If you look at the failed joint you can readily see that the glue has not penetrated the wood at all.It was very embarassing when a $400 chair fell apart.

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

View Steven H's profile

Steven H

1117 posts in 2523 days


#13 posted 04-23-2011 05:10 AM

LOOK dyes and pigment have not nothing to do with weakening the joint, it is the products that containing the solvents.
And other consideration is clamping pressure, the way you apply the glue, etc…

A thick layer of glue weakens the joint.
A thin, even layer of glue forms a strong bond.
http://www.provenwoodworking.com/wood-glue.html

How long are you letting the stain dry?

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Steven H

1117 posts in 2523 days


#14 posted 04-23-2011 05:13 AM

Another good point gfadvm
The stain can also prevent the glue from bonding properly.

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fussy

980 posts in 2514 days


#15 posted 04-23-2011 06:43 AM

Rich,

I have allways heard that glue is meant on go on bare wood. Oil-based stains-pigment stains-will affect the bond. I too like to prefinish, but I ALLWAYS tape my joints to keep them clean. William’s quick and dirty test above adds to that conviction. But, as a1Jim says, if it’s a small stress-free part, no worry. By the way, what kind of dowelling jig do you use, and how do you like it?

Steve

-- Steve in KY. 44 years so far with my lovely bride. Think I'll keep her.

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