Underpinning with wet or dried glue

[rudgey]

I have started gluing my frames and clamping them with a Besey overnight then unpinning when dry for nice clean results and better joints.
Before like most I would underpin with wet glue making a right old mess.

What way do you join your frames and why?

[Ultima Thule]

For decades used my Euro underpinner, with occasional recourse to an even older Morso,IIR, corner clamp and chop routed for keys but over the last few years have bought a Hoffman and wondered how I ever managed before without it. I have also got two Masterclamp cramps which although a lot slower than underpinning only wet, give a tight even finish that is essential with the popularity of plain and flat mouldings at the moment. I V nail the corners when dry as well.

[rudgey]

Yes I would very much like to buy a Hoffman when budget allows, not sure how long they’ve been out but you don’t see them secondhand at all. I do quite a lot of hardwood framing and would save all that time pinning etc.

[Justintime]

Hoffmann do come up quite often on eBay and Facebook Marketplace in various states of previous use from around the £1k+ mark.

[JKX]

I don’t know about better joins, I spent three or four grand on an underpinner and if that didn’t give perfect results I’d have sent it back!

I already knew it would before I bought it though.

There were always problematic mouldings of course but I still never glued, clamped, allowed to dry before pinning. Not once ever, and nor did I when I started out with tenon saw, vice and hammer & nails!

A band clamp AFTER joining on the odd frame maybe.

No “right old mess” either! I actually liked to see a bit of glue squeezing out of the mitre; the only issue would be getting the stuff in the underpinner block but regular maintenance makes that a non- issue

Pinning after the glue has dried, breaks the bond at those points as well.

[JFeig]

The basic theory of joining wood is to secure the pieces together while the glue dries. This can be done with a mechanical joint or fastener. It can also be done without a fastener.
Adding a fastener "when the glue is wet" will hold the wood together while it dries.
Adding a fastener "after the fact" does not hold the wood together while it is drying.
Adding a fastener "after the fact" will give added security to the joint in adverse conditions.
Adding a fastener "after the fact" can break the glue bond.

[pramsay13]

The point of an underpinner is to hold the two pieces of wood together while the glue is drying without the need for clamps or nails in the side where the holes can be seen.
The only time I clamp is on taller mouldings that struggle with stacked wedges.
Underpinning after the glue has dried will stress the join and maybe crack it, meaning the joint is only held by the wedges.
In 13 years I have never made a right old mess! If the glue squeezes out I just wipe it. I'm unsure how you can make a right old mess on the underpinner, but not when using clamps.

[rudgey]

You all make some good points, I do need to consider the possibility of cracking the joint after it has dried.
I’m doing a lot of high profile (as in size) box frames, that is why a like pulling the tops in with a band clamp.

The mess is from the glue dripping joints as I rotate them on the bench which supports the frame while underpinning.
I do however use a manual foot pedal Pistoriuos underpinner, which is very solid but not exactly state of the art..

I wonder if I could underpin with one of those small Stanley type cord strap attached? Or maybe I need to save for a new modern underpinner.

I do know one very experienced framer who is a top water gilder who has never owned one, has always done things the traditional way with pins and sells his frames for thousands.

[Justintime]

Too much glue hasn't been mentioned yet. Obviously you want as much of the joint to have a covering of glue as possible but using too much achieves nothing but cleanup work. I rarely have any glue coming out of joints. Carefully applying the right amount ensures that under pressure that blob spreads to cover the entire surface.
I hope I'm not being too harsh, but if you're not working in a clean and tidy way, then I suggest it's a skill to aim for. It's skilled work when done properly, which leaves little room for error and mistakes just eat away at the bottom line. I'm obviously talking more about prefinished mouldings. The hand finishers amongst us can throw paint around and cover anything up! But you still need clean hands and tools and work surface to turn from glueing frames to mounting and glazing art!

[JKX]

The mess is from the glue dripping joints as I rotate them on the bench which supports the frame while underpinning.
.

Maybe you need to do things differently, I hope you’re not glueing the ends of each length before you start joining; that’s how it sounds, although for production, you could.

Grab the first two sides to be joined, apply glue to one end of one of them- pin. There are two ends on the bench/supppprt but there’s no glue on them. Repeat with the other two sides

Apply glue to the ends of one of the ‘L’s you now have and place on the underpinner - THIS point is the only point that you will have a glued but un-joined end on your bench/support.

Join, turn the frame 180 degrees and join the last corner.

There may still be SOME glue from the base of the corners. but not if you’re careful, “dripping “ really should not be a thing though. Also cover areas like this with disposable material, like glass interleaving sheets.

Don’t get frame makers confused with picture framers!

[vintage frames]

Underpinning or cross nailing will hold the mitres together but if you want to get the strongest glue bond then a band clamp is essential in that the pressure achieved forces the glue deeper into the cellular structure of the wood.

[NTG999]

Another question maybe what glue?, I use Titebond, a runny PVA won't help. Generally on a prefinished moulding I aim for no glue 'escaping'. When I use solid woods; oak ash etc I am more liberal.
Glue then underpin, strap clamp if a tall moulding

[rudgey]

Thanks for all your advice, it was interesting to hear how little glue you’re using.
I’m using Titebond but putting a good smear on all the ends, that’s where I have been going wrong, too much and all at the same time.
So most of you are only putting a few blobs on one side? I was worried it would just get drawn in by the end grain and not be strong enough.

Can I also ask if underpinning a large L shape profile black finished not raw timber, would you also pin the tops of the L?

[Justintime]

As said by JKX, glue just on one side of each corner. With the flat spout on the 8oz bottle you can blob or run a line of glue. The advice is glue it and put it together, if you have to separate it again add a drop more. If you're not convinced, cut glue and join a few scraps leave for 3 days and try to pull apart!
L shaped, if you mean underpin the top no it's going to show, if you mean headless pin it I'll leave that to the headless pinners. I'm fortunate to have a Hoffmann, but unless it comes out super tight I'll often strap clamp the top. Always on larger tray frames. Glueing under pressure(strap or band clamp) is the strength that joins the wood, underpinning is the emergency backup in case that joint fails in the future is how I look at it. Belt n braces. Most mass produced imports only underpin and we've all seen how that turns out.

[rudgey]

Thanks that confirms things for me

[prospero]

I've always considered pinning after the glue is set a bit counter-intuitive. V-nails are essentially internal clamps.
Clamping a joint after the glue has set is a bit bonkers in my book. Underpinning is a quite violent process and can
actually weaken or even break a dried glue bond.