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"Open time" versus "Grab time"

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Forum topic by richgreer posted 01-18-2012 05:12 PM 1113 views 0 times favorited 17 replies Add to Favorites Watch
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richgreer

4524 posts in 1733 days


01-18-2012 05:12 PM

With respect to glues, we probably all know what open time is. A longer open time gives us more time to arrange pieces for assembly before the glue dries.

I’d like to define what I call “Grab time”. If you are putting together a joint like a sliding dovetail and others, once the two pieces of wood, with glue, come together, they start to bind. Within a relatively short period of time (much less than the open time) they will bind to the point that you can no longer move the joint further together. I call that the “grab time”. It is essential that the joint be fully seated before you reach the grab time.

Tite Bond 3 is my standard glue. It claims to have a 10 minute open time. I’ve never timed it, but it seems like it’s grab time is about 1 minute.

Sometimes I am doing a rather complex assembly and I have to pull several M&T joints together at the same time. I know I have got to get all the joints fully seated, all the way in, before the end of the grab time. I recently did an assembly step where I needed to bring 4 M&T joints together at the same time. It did not go smoothly and one of the joints ended up about 1/8” shy of being fully seated. IMO, that ruined the piece and wasted quite a bit of QSWO.

I say all this to say that: (1) I wish the glue manufactures would put more emphasis on increasing the grab time as opposed to the open time and (2) I wish there was more information available about grab time of different glues. I have never read anything that tells me about how grab times differ from glue to glue.

If I had the extra time, I would conduct an experiment to measure grab time on different glues. It would be great if some magazine conducted such an experiment and published the results.

Has anyone seen information on, what I call,the grab time of different glues?

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


17 replies so far

View Bill White's profile

Bill White

3457 posts in 2619 days


#1 posted 01-18-2012 05:32 PM

I have been using Gorilla PVA for a while. Was using TB III until I read (somewhere) about its tendancy to “creep”. Never had a failure with either glue and, like you, I’ve never timed the grab. I guess that I’m a weeny ‘cause try to let my glue-ups rest at least overnight unless I’m usin’ pocket screws.
Bill

-- bill@magraphics.us

View dbray45's profile

dbray45

2509 posts in 1435 days


#2 posted 01-18-2012 05:38 PM

Just so you know, Titebond III will fail if you heat the joint up. Titebond II is more heat resistant dut is not watter resistant.

I know of what you speak. When I assembled my cart made from ash, there were several joints that had to seat at the same time. It took 4 or 5 dry assemblies to come up with a sequence that I could use to minimize the grab. A cull with a dead blow hammer or a clamp to bring it in tight – again, use a cull so you can add more pressure – makes up the difference.

-- David in Damascus, MD

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kaschimer

89 posts in 1048 days


#3 posted 01-18-2012 05:44 PM

I was watching a WoodWhisperer video the other day, and he was doing something similar, where he needed longer time to make sure everything is aligned. I believe he used Epoxy glue in those cases, and regular wood glue (like Titebond) for everything else that didn’t need longer to assemble.

Having said that, I couldn’t tell you what the “grab time” was of the Epoxy, only that it was enough for him to complete assembly of the complex stuff.

-- Steve, Michigan - "Every piece of work is a self portrait of the person who accomplished it - autograph your work with excellence!" - Author unknown

View Greg..the Cajun  Box Sculptor's profile

Greg..the Cajun Box Sculptor

5113 posts in 1967 days


#4 posted 01-18-2012 06:22 PM

I know what you mean about the grab time being shorter…and that is one reason I also use epoxy on some projects. I also like the epoxy better for gluing miters on my boxes because of better holding power on end grain.

Titebond III is a great glue but you do have to work fast…and I like to take my time to ensure everything is lined up and glued up properly.
I would also like to see a comparison and review of grab times as opposed to open times.

-- If retiring is having the time to be able to do what you enjoy then I have always been retired.

View DS's profile

DS

2131 posts in 1079 days


#5 posted 01-18-2012 06:25 PM

I have discovered that Grab Time varies proportionately with the size of your dead blow mallet.

-- "Hard work is not defined by the difficulty of the task as much as a person's desire to perform it.", DS251

View TheDane's profile

TheDane

3794 posts in 2321 days


#6 posted 01-18-2012 06:32 PM

Rich—I know what you mean … I ran into this when I built my Morris chair. I don’t like to do a partial or sequenced glue-up of a frame … too hard to square up rails and legs/stiles if one end is already glued and dry.

By the time I got the last through-tenon buttered with TiteBond III, the first two were getting tacky and I had a heck of time pulling all four joints together and squaring the assembly.

—Gerry

-- Gerry -- "I don't plan to ever really grow up ... I'm just going to learn how to act in public!"

View DS's profile

DS

2131 posts in 1079 days


#7 posted 01-18-2012 06:35 PM

Gerry, If you dilute your glue slightly, or even pre-wet the joint on the first few joints, it should prolong the amount of time you have to complete the glue up before the glue grabs.

Some glues, when I know the tack time, I start an egg timer and check my progress as I go. This is mostly for complex glue ups.
When I run my veneer press, I always run the timer. I know that from start, to pulling a vacuum in the bag, I have exactly 12 minutes. This lets me know when to stop fussing with it and get busy.

-- "Hard work is not defined by the difficulty of the task as much as a person's desire to perform it.", DS251

View bugz's profile

bugz

773 posts in 1322 days


#8 posted 01-18-2012 06:45 PM

I have switched to epoxy on tuff glue ups and use titebond III on all else. I also have got to last joint in a tough glue up and could not get last joint all the way together. But also on softer woods, the longer the wood is exsposed to the glue [titebound III ] the more swelling of the wood fibers. That is what got me changing to epoxy. I also agree that grab time is 1 min. for titebond III. All tough glue ups, I recruite my sweety to help. She has learned that we only have a minute or two, then my atitude starts to deteriate. Also I have been puting some bowties in on some slabs with cracks and I use epoxy, I think it helps fill voids. Also with epoxy, after it is mixed I can stir in some fine sawdust to add color.

-- Bob, Lewistown, Montana. Kindness is the Language the blind can see and deaf can hear. - Mark Twain

View TheDane's profile

TheDane

3794 posts in 2321 days


#9 posted 01-18-2012 06:47 PM

DS251—Hmmm … never really thought about that.

It would seem that diluting the glue could weaken the joint, and pre-wetting the joint might cause the wood to swell. No?

—Gerry

-- Gerry -- "I don't plan to ever really grow up ... I'm just going to learn how to act in public!"

View DS's profile

DS

2131 posts in 1079 days


#10 posted 01-18-2012 06:52 PM

Gerry, correct on both counts. But it is a matter of degrees.

You are just trying to shift the glue up a bit more in your favor. Slightly diluted, lightly wetted. Glueing wets the joint anyway. We’re talking a small percentage more wet. That’s all.

Experimentation on scrap wood is totally acceptable also. I usually mock up my joints with scrap as I setup my tools. That same scrap can test your glue’s tack time.

-- "Hard work is not defined by the difficulty of the task as much as a person's desire to perform it.", DS251

View TheDane's profile

TheDane

3794 posts in 2321 days


#11 posted 01-18-2012 07:02 PM

DS251—I see what you mean. I do actually do experimentation … sometimes to the extent of building prototypes if I am getting into something that is new to me.

We’re downsizing a bit (getting ready to sell the house and move), and while clearing off a shelf in the storage loft above my wife’s car, I found a set of frame and raised panel doors I made over four years ago when I was building my entertainment center. Usually the prototypes are just cut up for other work or go into the scrap bin, but these (must have) turned out so well I dry-assembled and wrapped them in plastic. Now I’m trying to figure out what I can build that would use a set of pine raised panel doors!

—Gerry

-- Gerry -- "I don't plan to ever really grow up ... I'm just going to learn how to act in public!"

View DS's profile

DS

2131 posts in 1079 days


#12 posted 01-18-2012 07:15 PM

FWIW, I use Titebond II almost exclusively. Titebond III is probably superior in many ways, (especially for joints exposed to weather or moisture), but 1 to 2 minutes tack time? That sounds rediculous.

T2 usually gives me quite a bit more time. Wish I could say exactly, but there are so many variables that a range is probably better suited. I’d guess 6 to 10 minutes. Once it is under clamping pressure, full tack time is about 15 minutes—hard to get apart by that time.

Glue ups are like a stage play. I rehearse them to minimize wasted movements. It is preplanned. All the cauls are ready, all the clamps set at the right distances and there’s no interruptions once there’s glue open.

-- "Hard work is not defined by the difficulty of the task as much as a person's desire to perform it.", DS251

View Jim Bertelson's profile

Jim Bertelson

3664 posts in 1823 days


#13 posted 01-18-2012 07:22 PM

Having dealt with these issues recently, appreciate the discussion. Using Titebond III I leave a little water in my glue brush to help wet the glue when I anticipate problems.

-- Jim, Anchorage Alaska

View richgreer's profile

richgreer

4524 posts in 1733 days


#14 posted 01-18-2012 07:30 PM

This is excellent input. Thank you.

I have never considered Epoxy for woodworking. I will now. Also, I never would have expected TB2 to have a longer “grab time” than TB3. TB3 has the longer open time.

I had also not considered diluting the glue with a little water. Does anyone know if that weakens the joint to any significant degree?

This discussion proves the value of our website. Raise an issue/problem and you almost always get good feedback and insight. that can be of value to many.

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

View pintodeluxe's profile

pintodeluxe

3365 posts in 1472 days


#15 posted 01-18-2012 08:25 PM

I have gone to Titebond II Extend for all of my complicated glue-ups. It has an open time of 20 minutes, and it will allow you to reposition the joint as needed. It is a little runny compared to regular Titebond II, but for me it is worth it to know I can relax and glue-up assemblies with a dozen mortise and tenons at one time. Glue strength in my testing is stronger than the wood fibers of white oak (same as regular Titebond II).
Titebond II Extend comes in a white container, and is available in several sizes, including gallons. It is available through Amazon.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

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