Glue-ups, surface flatness, anxiety, and 100X-200X magnification

[Al Navas]

On a previous post at another woodworking forum, a friend commented that removing the glue prematurely will lead to starving of the glue line.

He was right, of course. And I have photo evidence. Please read on.

From my blog:

I truly must stop reading Christopher Schwarz's blog. First, it cost me $20 for the first copy of the EyeClops. Once I learned what a terrific "toy" it is, I bought another one (this one for $28, as the price went up) for use by our granddaughters.

But now I am glad I bought two copies of this very special toy!

Recent discussion on glue-ups, particularly the table top I have been working on, highlighted to me why it is important to wait to clean the glue until it has gelled well. If one rushes to clean, as I did due to anxiety (to measure table top flatness), the glue line is starved near the surface, as it shrinks.

This first photo shows what the glue line should look like, if one waits:

http://sandal-woodsblog.com/wp-content/uploads/2009/02/good-glue-line.png

But, by cleaning the glue at the glue line, voids in the glue line develop - the glue shrinks as it dries and cures:


http://sandal-woodsblog.com/wp-content/uploads/2009/02/glue-line-void.png

My woodworking friend "rhino", on this thread on WoodNet, was 100% correct. Of course, I knew this was likely to happen, but anxiety does funny things in the heat of a critical glue-up.

While the EyeClops was in the shop I looked at other features on the table top surface. This one is a small crater, part of a tiny knot near one of the ends of the top:

http://sandal-woodsblog.com/wp-content/uploads/2009/02/small-wood-knot.png

The side grain on the quarter-sawn white oak looks like this:

http://sandal-woodsblog.com/wp-content/uploads/2009/02/side-grain-on-qswo.png

Focusing is critical using the EyeClops. And it requires a steady hand, to get good photos. But, once this is learned, it is very easy to use:

http://sandal-woodsblog.com/wp-content/uploads/2009/02/eye-clops-in-use.png

Chris, thanks for finding this little treasure!


Al

[Bruce Page]

That’s an interesting gadget Al but if it takes 100X to see the glue line “dip” then it really isn’t that important is it? :confused:

[Al Navas]

I think you are right, Bruce. But, if cleaned too aggressively, it is possible the finish won't be able to fill in completely, as our friend rhino found (the WoodNet thread). I still think it is best to wait until the glue has gelled well, as shrinkage beyond that point may not be too great.

If anyone else has an opinion, I would love to read it here. Thanks!


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[JohnT Fitzgerald]

Al - that's a pretty neat gadget. might be interesting to look at the ends of sharpened edges (chisels, etc) - before & after, microbevel, etc.

[David Keller NC]

"I still think it is best to wait until the glue has gelled well, as shrinkage beyond that point may not be too great."

While I don't disagree with you that patience is a good thing, I rather doubt that what you're seeing is something that will ever cause a significant problem. I'm a photgrapher and engineer, and can tell you that any close-focusing magnification system, whether the rather cool toy you've got or a very expensive microscope has an exceptionally short focal plane - on the order of a few thousandths of an inch.

It's doubtful the "glue crater" you found is very deep, perhaps a few tens of thousandths of an inch. Whatever film finish you put on the top will easily fill that, especially if it's a slow-set finish such as varnish or polyurethane.

[Al Navas]

THAT is why Christopher Schwarz got it in the first place, I think. It is a neat tool! You might want to read his blog; search for eyeclops when you reach the Woodworking Magazine blog.


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[Al Navas]

...It's doubtful the "glue crater" you found is very deep, perhaps a few tens of thousandths of an inch. Whatever film finish you put on the top will easily fill that, especially if it's a slow-set finish such as varnish or polyurethane.
David,

Hello, fellow photographer and engineer!

In my case, you are right.

However, my friend rhino, over at WoodNet, has stated that he cleaned the glue too aggressively, and Waterlox was unable to fill in the voids at the glue line.

In the prototype tables I built, I also cleaned the glue line, to check for flatness, as I was to show the client the little tables. And the finish did fill completely at the glue line. In fact, satin finish does a great job!


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[Jamie Buxton]

Tell us about that Eyeclops thing. I found a web site which suggests that I'd need to have a TV in my shop to use the Eyeclops. Is that true?

[Tom Veatch]

Uh uh!!!

My stuff looks rough enough already without subjecting it to 200X magnification. Leave me my fantasies, PLEASE!

[Alan Tolchinsky]

Hey guys, If you're going to start using magnification in WW'ing then I quit the hobby. I know my work won't stand up to it let alone a good pair of eyes. Myself, I always remove my glasses when looking at my work. :p

[Chris Padilla]

I make sure the sun or a strong light is in their eyes so that people have to squint when they look at my work.... ;)

[Al Navas]

Tell us about that Eyeclops thing. I found a web site which suggests that I'd need to have a TV in my shop to use the Eyeclops. Is that true?
Jamie,

The EyeClops has its own small screen - I believe it is about 2 inches on the diagonal, good enough for me. No TV needed in the shop. Of course, you could always bring in the work to your living room...:D In my case, Sandy would make sure I slept outside, in one of two igloos, with the cats.


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[Al Navas]

Hey guys, If you're going to start using magnification in WW'ing then I quit the hobby. I know my work won't stand up to it let alone a good pair of eyes. Myself, I always remove my glasses when looking at my work. :p
Alan,

It is scary when you start looking at edges you think are sharp. Like everything else, one must keep a certain perspective on things - and this IS a thing.:eek: For example, our granddaughters wondered why some of the photos were turning out too dark. Questioning a little bit revealed they were trying to take photos of boogers...:rolleyes:


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[Al Navas]

I make sure the sun or a strong light is in their eyes so that people have to squint when they look at my work.... ;)
Chris,

The brighter, the better. And, of course, using strobe lights works even better.:D


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[Peter Quinn]

So,...........to my eyes, as dismal as they are these days, the glue line in the QSWO seems to be only a fraction of the grain lines, and IME the finish in open pored woods is NOT going to to fill the grain easily without grain filler.So if you want a smooth finish, you will have to fill the grain anyway. Of course using a grain filler to fill grain will result in highlighting natures random pattern or not depending on the color of the filler, where as filling a glue joint will create a long straight line that is the tell tale sign of shoddy workmanship. And shoddy workmanship is something i have much personal experience with!:D

Magnifying the defects to that level while perhaps fun is of little interest to me on a practical level as I do not scrape glue too early and I prefer to use the only instrument through which my work will regularly be viewed, i.e. MY EYES! Still cool to see it up close though, thanks for those images. But it can't be seen with the naked eye, it ain't there in my world. I have also scraped glue too late, and in some species, oak for instance, this will tear bits of wood from the glue joint which you don't need a microscope to see. Anybody else been there? i have been taught to clean up those glue lines at that nebulous perfect moment where the glue has not yet hardened but is no longer wet either, sort of like pudding skin to the middle and crispy on the out side. Haste makes waste, and a lot more work too.

One place where I do like the magnification is when sharpening a hand saw. I took a class with Mario Rodriguez in cutting dovetails, first step was to prepare a saw. We had to turn a cheep 24TPI dovetail saw into an effective 12TPI rip saw by eliminating every other tooth, adjusting the set and sharpening each new tooth. For this 20X magnification using jewler's glasses was critical. I wonder if 100X would be even better to hone those teeth to perfection?

[David DeCristoforo]

This is great to know since virtually all of my customers whip out their 100X magnifying glasses as soon as they come into the shop. BTW, at 100X a flea's head is about the size of a football. Let's see now... where did I put that hair I was splitting? Hey AL, could I borrow that gizmo for a sec?

Teehee

[Jamie Buxton]

Jamie,

The EyeClops has its own small screen - I believe it is about 2 inches on the diagonal, good enough for me. No TV needed in the shop. Of course, you could always bring in the work to your living room...:D In my case, Sandy would make sure I slept outside, in one of two igloos, with the cats.


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Where did you get yours? This site -- http://www.eyeclops.com/ -- seems to sell things which don't quite look like the object in the original post in this thread, and seem to require a TV.

[Al Navas]

...the glue line in the QSWO seems to be only a fraction of the grain lines, and IME the finish in open pored woods is NOT going to to fill the grain easily without grain filler...
I did a good job, didn't I? :D




... One place where I do like the magnification is when sharpening a hand saw. I took a class with Mario Rodriguez in cutting dovetails, first step was to prepare a saw. We had to turn a cheep 24TPI dovetail saw into an effective 12TPI rip saw by eliminating every other tooth, adjusting the set and sharpening each new tooth. For this 20X magnification using jewler's glasses was critical. I wonder if 100X would be even better to hone those teeth to perfection?
Peter,

Maybe your limit will be the quality of your stones? I don't know. But I BET it will be extremely helpful there.





This is great to know since virtually all of my customers whip out their 100X magnifying glasses as soon as they come into the shop. BTW, at 100X a flea's head is about the size of a football. Let's see now... where did I put that hair I was splitting? Hey AL, could I borrow that gizmo for a sec?...

To quote you, David, teh heh... :D By the way, the glue line is right about the size of two gnat's butts. Pretty small, anyway...:cool:

Ahhh - and to think I have done it all in the name of science! :rolleyes: But someone has to do it.


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[Al Navas]

Where did you get yours? This site -- http://www.eyeclops.com/ -- seems to sell things which don't quite look like the object in the original post in this thread, and seem to require a TV.
Jamie,

Try Amazon. It is the EyeClops Bionicam . Sorry - I left out the BioniCam part. It makes a difference! You can buy it at Amazon.com .


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[Alan Tolchinsky]

Alan,

It is scary when you start looking at edges you think are sharp. Like everything else, one must keep a certain perspective on things - and this IS a thing.:eek: For example, our granddaughters wondered why some of the photos were turning out too dark. Questioning a little bit revealed they were trying to take photos of boogers...:rolleyes:


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Al, The granddaughters sound like they're very imaginative. :D

[Al Navas]

Alan,

They are all home schooled. Our daughter asked me to do science. And chemistry really gets their attention.

Last week we did several experiments that resulted in slime, and later, after two more stages, the slime can be converted into a super-bouncy, rubbery material. Well, there is rubbery material all over the kitchen now, since they have the procedure down pat...:D


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[Chip Lindley]

These LONG Winters do take their toll!! Claustraphobic Paranoia is at its worst under 200x magnification!

Latent side effect: Incessent babbling about *toys* in a woodworking forum! *tisk tisk*

[Al Navas]

...Incessant Wonderful babbling about *toys* in a woodworking forum! *tisk tisk*
Chip,

There you go - I corrected it... :D

Maybe we should start talking about the latest sanding block....:cool:


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[Mike Wilkins]

Now I know why I sometimes get straight depressions along the glue line after the part is dry. It does not show up until applying a finish, which leaves a long crater. Thanks Al.

[Al Navas]

Mike,

You just made my day - thanks for sharing!


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[Rob Diz]

Al sorry for the delay in finding this post - I'm the guy (rhino) that may have started this debate about the shrinking glue line.

I will try to take a few pictures, but I can tell you I glued up two wide curly cherry boards for a top on a sofa table. It was one of my first "fine" furniture projects, and I was concerned that I would have glue residue left over and ruin the finish on my top - so I was very aggressive with a wet sponge.

I applied BLO, then padded on a seal coat of garnet shellac, then wiped on Waterlox sealer. I was unable to get the craters along portions of the glue line to fill in. In part, that may be due to the fact that I wiped on my finish and did not leave enought to "level" into the glue line gap. The gaps are visible to the naked eye (if you look at the top with a raking light). Most non-ww who look at the top will never see the issue. Of course, it has bothered me for a long time, and changed the way in which i clean up my glue lines (I wait longer, or even wait until the glue has dried)

I can swear on a stack of bibles that glue line shrink is not a theoretical question like whether my jointer blades are .00001 too high - this was a practical issue with real implications to my first project.

[James White]

Although I agree. Leave the glue and scrape it off later. I was just wondering if the crater Rob is describing. Is due to using water to get the glue off. Therefore swelling the wood in that area. Then it all gets sanded flat. Then when the water eventually dries the wood shrinks and causes the crater. I am not saying this is the case. More or less just thinking out loud. Perhaps one of the more experienced members can comment.

James

PS: I think the toy is pretty darn neat. If I had some spare cash I would spring for one.

[Al Navas]

Thanks for pitching in, Rob! Good to see you on SMC.


James,

What you describe is one of the things that can happen (typically, on thinner boards than mine for this table top) if one uses biscuits, for example, as an aid to align boards when doing edge glue-ups. The glue swells the biscuit, the slot cut for the biscuit now contains much more water than the area/volume around it, and a "bump" on the surface reveals where the biscuit(s) is/are.

So as to not cause a dip on the surface, you must now wait for the glued up boards to reach equilibrium moisture, which could take days. Why? Because, if you sand right away, and level the surface, a dip is likely to develop where the biscuit(s) is/are, as the wood in the glued up boards dries to equilibrium.

I suspect what happened to Rob is comparable. Of course, other factors may contribute, too, such as jointing and excess gaps, etc. However, Rob has so much experience that I believe it was partially the finish schedule he used that failed to fill the voids. Waterlox goes on very thin, so this makes sense.

I welcome others' opinions, especially now that Rob has clarified this for us on THIS forum.

Thanks, Rob!


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[Chris Padilla]

Al sorry for the delay in finding this post - I'm the guy (rhino) that may have started this debate about the shrinking glue line.

I will try to take a few pictures, but I can tell you I glued up two wide curly cherry boards for a top on a sofa table. It was one of my first "fine" furniture projects, and I was concerned that I would have glue residue left over and ruin the finish on my top - so I was very aggressive with a wet sponge.

I applied BLO, then padded on a seal coat of garnet shellac, then wiped on Waterlox sealer. I was unable to get the craters along portions of the glue line to fill in. In part, that may be due to the fact that I wiped on my finish and did not leave enought to "level" into the glue line gap. The gaps are visible to the naked eye (if you look at the top with a raking light). Most non-ww who look at the top will never see the issue. Of course, it has bothered me for a long time, and changed the way in which i clean up my glue lines (I wait longer, or even wait until the glue has dried)

I can swear on a stack of bibles that glue line shrink is not a theoretical question like whether my jointer blades are .00001 too high - this was a practical issue with real implications to my first project.

Rob,

Did you use biscuits in the edge glue-up? Do you recall how long after glue-up that you sanded the top?

I'm getting at a couple things here and Al already tackled the issue with using biscuits (moisture concentration, swelling, adequate time to dry, etc.) but the same thing may have happend with your agressive wet sponge on the joint. Gluing a joint already adds moisture to a very small area and you may have added more with aggressive wiping along with removing too much glue.

[Rob Diz]

No biscuits were killed during my glue up. It was 3/4 stock, and I was actually able to get the boards to match up well, with a touch of a spring thanks to my then newly acquired #4. The only time I have used biscuits so far is with ply shop grade projects, although I may use them to align my upcoming slab glue up due to the thickness of the stock.

My recollection (and it's been a few years) is that I scraped the glue line the day after the glue up with a card scraper (or maybe a #80), and then started the finishing process.

Oh, I tried to capture the defects on camera, but have not been able to get a good shot.

[Matthew Hills]

So is the issue really that the glue shrinks, or is it that you remove glue from the gap when you wipe off the excess? (i.e., take the hypothetical situation of trying to "level" off the frosting of a chocolate cake -- quite likely that even a superficial swipe of a finger will end up tearing out frosting as the top frosting adheres to the lower frosting)

Matt

[Dan Hahr]

Here's my understanding of it. If you use a scraper on the joint before the moisture is gone, you run the risk of removing wood that has swelled proud of the surface. When the moisture leaves, the joint shrinks and there is a slight depression in the surface. No problem for me as I usually remove plenty of wood in the final surfacing.

If you wipe the glue line, (not scrub it with a sopping wet sponge), you level the glue with the surface. It then dries and shrinks, leaving a slightly concave surface.

I just examined several glue lines on various items of oak furniture I made (some old, some newer). All of the lines were practically invisible to the naked eye, except for where the grain varied. Under magnification, I could see a hint of a darker color along the line, but no gaps. I used a needle to "feel" the glue line and could not.

I use a jointer and make sure the last pass is very slow. Sometimes I take off a thousandth or so with my block plane just for fun. It seems to take the imperceptible scallops off. I use lots of glue, and usually shave it off with a chisel after it sets but is still soft (not wet). Sometimes I do it several days after it dries. Sometimes, I wipe it off with a credit card if it is too runny. I use home brew wipe on varnish or just a danish oil blend.

This may sound harsh, but I think that those who can see their glue line are not properly preparing their joints or applying the glue properly. Glue Line Rip does not factor in user error, or tablesaw misalignment. I don't have a microscope, but if my glue lines looked like those photos, I'd have an aneurism.

I'll be taking a few samples to the lab. You may never hear from me again....
Dan

[Al Navas]

So is the issue really that the glue shrinks, or is it that you remove glue from the gap when you wipe off the excess? (i.e., take the hypothetical situation of trying to "level" off the frosting of a chocolate cake -- quite likely that even a superficial swipe of a finger will end up tearing out frosting as the top frosting adheres to the lower frosting)...
Matthew,

I have never glued two boards using frosting... :D But it sounds delicious! In this case I believe it is mostly that the glue shrinks as it dries.







Here's my understanding of it. If you use a scraper on the joint before the moisture is gone, you run the risk of removing wood that has swelled proud of the surface. When the moisture leaves, the joint shrinks and there is a slight depression in the surface. No problem for me as I usually remove plenty of wood in the final surfacing.

If you wipe the glue line, (not scrub it with a sopping wet sponge), you level the glue with the surface. It then dries and shrinks, leaving a slightly concave surface...
Dan,

You are correct. That is the reason I wiped, instead of scraping. The wood is already soft(er) at the glue line.




...I just examined several glue lines on various items of oak furniture I made (some old, some newer). All of the lines were practically invisible to the naked eye, except for where the grain varied. Under magnification, I could see a hint of a darker color along the line, but no gaps. I used a needle to "feel" the glue line and could not...
I tried the needle as a "feeler gauge", and cannot feel anything, either. I believe the tip is too large for such a small gap. In the photos above, the glue line is just about imperceptible to the naked eye.






...This may sound harsh, but I think that those who can see their glue line are not properly preparing their joints or applying the glue properly. Glue Line Rip does not factor in user error, or tablesaw misalignment. I don't have a microscope, but if my glue lines looked like those photos, I'd have an aneurism...
You are harsh, Dan :D :D . Just kidding!!! Never a thought - your comments are great! David Keller, in his comments above, indicated how exaggerated the photos make the whole thing look. We are talking about "craters" that are just about invisible to the naked eye, even close up. And the finish does away with just about all of them, anyway.





...I'll be taking a few samples to the lab. You may never hear from me again....
Y'all come back... I look forward to your results.


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