This is not really a joinery question but this seemed to be the most logical location for a post. When edge gluing 2 pieces of wood how long do you allow the glue to dry before you begin to work w/ the new panel?
Thanks,
dlb
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The undisciplined life is not worth examining.
Replies
It depends on the glue.
Using PVA I've got away with getting the panel out of the cramps after half an hour followed immediately by running the panel over and under planers. It's not recommended as leaving assembled glue-ups 'overnight' is the normal advice.
Urea formaldehide type glues need at least 4 hours at approximately 20ºC
Polyurethane types need 'overnight'.
Hide glue, hot or liquid is another that needs 'overnight'.
Epoxy resins vary quite a bit depending on their designed open time and cure speed-- anywhere from at least five or six hours to 24 hours or more.
That covers a reasonable range of the many likely glues easily available to amateur woodworkers that you might be asking about. Slainte.
Richard Jones Furniture
What about the concern that the added moisture from glues like PVA can swell the wood at the joint, so that if planed or sanded too soon a "micro depression" could be created at the joint line when the pieces completes the drying process? That would suggest unclamp when you need to, but don't plane or surface until at least overnight.
Steve, you're quite right about creating slight depressions after the moisture has evaporated. This has happened to me more times than I can count. Even though I'm well aware of the problem, the ticking clock often sends parts through the planer or wide-belt within hours of glue-up.
David Ring
http://www.touchwood.co.il/?id=1&lang=e
You're correct Steve. I don't know if you're picking up on something I've discussed in this forum a few times before, or if you've observed the phenomenom in your own work, but in either case it's a legitimate concern. Perhaps you're prompting me to yet again discuss the subject?
Furrows at the glue line can be a problem, as can oval depressions that reveal the placement of biscuits if these are included in the edge joint. Dowels too can show, and if there are are other forms of edge joint reinforcement such as tongues, etc, then similar concerns are legitimate. And, as you rightly point out, it's the water in certain glue types that's the cause as it swells the wood at the join line. The wood, after swelling needs some time to dry and shrink down again to match the wood in the rest of the panel.
On the other hand, as David said in the subsequent post to yours, sometimes 'needs must' so to speak. Getting away with hurrying up on the cure time depends where the panel is going. Internal panels for instance aren't generally a problem if they're furrowed. Visible vertical panels might be a problem-- it depends how the light reflects and refracts off the polished surface. Horizontal panels show any furrowing most of all because theree's the greatest chance of low angled light sources revealing the maker's hurry-up job. And the glossier the polish the greater is the tendency of any faults, such as this, to reveal themselves.
This is the reason why I always recommend to learners that edge joined solid wood table and cabinet tops are left at least three days between glue up and polish preparation, and a week is even better. That recommendation suggests some essential planning is required, ie, don't leave putting together panels that will be horizontal parts until the last minute.
The original question didn't offer a lot of information, so I blasted out a few answers. I was hoping my response might elicit something more specific, such as type of glue used, the purpose of the glue up, etc, as that would lead to a response better tailored to the specific needs of the job. Slainte.Richard Jones Furniture
Steve & All ,
I feel the same ,I may un clamp after due time but will not surface
until full cure drying . Glue type plays a role as well .
d
Dusty,
This may seem like an odd question but if you are not going to surface them until full cure time why even waste the time to unclamp them after an hour?
Bio
Hiya Bio ,
To answer your question why unclamp , in my case I do so to free up the clamps for other panels or whatever . I have about 30 or 40 pipe clamps but on a job where I may create 40 - 50 or more panels I can get many panels glued up and ready for surfacing by using this method.
regards dusty
After I asked the question I assumed your rationale behind it.
Bio
Thanks for the reply. I was glueing up 5/4" soft maple w/ PVA glue. I let it sit for 4.5 hours before removing the clamps. I needed to continue working after that time but was curious if the panel would with stand planeing. It seemed to have held together quite well. I did notice that there was a slight depression along the glue line but planeing and sanding took care of that.
Thanks again,
dlb
.
The undisciplined life is not worth examining.
It usually takes a few days at least after a panel is polished and in service for the furrows to show up. At most it takes a few weeks before they are noticeable. This happens because the swelling at the joint, induced by the water in the glue, isn't given time to shrink back down prior to final flattening, sanding and finishing. It's the reason for it being generally best to leave the glue up at least a few days between glue up and polish preparation.
I'm curious about the depression you described seeing so soon after assembly and prior to applying polish. I wonder if, in fact, what you desribed was a slight ridge between one board and the next rather than a furrow? Slainte.Richard Jones Furniture
Thanks for the reply. You are correct concerning the ridge.
Thanks again,
dlb
.
The undisciplined life is not worth examining.
I try to get at any squeeze-out as soon as it's fairly solid but not fully cured. It's a lot easier to get off at that point. Other than that I try to go the full 24 hrs that most labels recommend. With PVA that sweet spot for squeeze removal around an hour, and epoxy around 5-6. IIRC, poly was around 4 and I dont remember how long it took with urea.
If you build it he will come.
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