Spruce Patches - Glue Size or not Glue Size

[floptimist]

      Hi all, I started glue sizing my spruce patches after reading "A New Look at Patch Fitting" by Joseph Grubaugh and Sigrun Seifert. The article mentions it in passing: "When the fit is nearly perfect, it may be desirable to glue-size the patch, at least on the end grain."

I can't think of a reason to not glue-size, except for the extra time and effort. Am I missing something? Any interesting takes on when glue-sizing a patch is critical and when it should be avoided?

[Don Noon]

The endgrain is porous, so if you don't glue size, you will likely have missing glue.  And the endgrain is where you need the bond to be as strong as possible.

Crossgrain, spruce is pretty weak, and not porous, so I don't think sizing is necessary.  Shouldn't hurt anything, though.

edit:  For a soundpost patch, where wood is scooped out and the patch is carved to fit, you don't get much of a clear distinction between what's engrain and what's not, so sizing the whole surface seems like a good idea.

[floptimist]

51 minutes ago, Don Noon said:

The endgrain is porous, so if you don't glue size, you will likely have missing glue.  And the endgrain is where you need the bond to be as strong as possible.

Crossgrain, spruce is pretty weak, and not porous, so I don't think sizing is necessary.  Shouldn't hurt anything, though.

Yes, it makes a lot of sense to me. The counterpoint is that for some reason it's not necessary? Because the endgrain is cut at a slope?

I get that the slope provides a not-as-pourous surface for the glue to adhere to. Every other endgrain joint in the instrument gets glue sized though, except maybe the purfling channel, so wouldn't glue sizing a patch be the norm?

[Nick Lewis]

Are you talking about a soundpost patch? Or a cleat? Cleats don’t get glueing surface on endgrain so not sure where that would be coming from. 

[Nick Lewis]

Never mind, saw you have this tagged as soundpost patch. Somehow I was reading it as a cleat question. 

[Brad Dorsey]

I think that the logic for sizing the end-grain areas of the patch applies equally to the end-grain areas of the patch bed.  So, if you’re going size one of them, you should size both.  And you should size and gently scrape the bed before starting to fit the patch.

I don’t size either, in the usual sense.  But, when I glue a patch, I make several glue applications to the end-grain areas of both to try to ensure that they are filled with glue.

[Jeffrey Holmes]

18 hours ago, floptimist said:

      Hi all, I started glue sizing my spruce patches after reading "A New Look at Patch Fitting" by Joseph Grubaugh and Sigrun Seifert. The article mentions it in passing: "When the fit is nearly perfect, it may be desirable to glue-size the patch, at least on the end grain."

I can't think of a reason to not glue-size, except for the extra time and effort. Am I missing something? Any interesting takes on when glue-sizing a patch is critical and when it should be avoided?

Very good article. Joe and Sigrun are wonderful makers and restorers.

I like the track system they suggest for soundpost patches as well.  Keeps the orientation of the patch very reliably.

I tend to glue size the patch and adjust the fit (again) before gluing it in.  It's possibly "mentioned in passing" as many do so as a matter of habit  (although certainly not everyone).

 

 

[floptimist]

12 hours ago, Jeffrey Holmes said:

Very good article. Joe and Sigrun are wonderful makers and restorers.

I like the track system they suggest for soundpost patches as well.  Keeps the orientation of the patch very reliably.

I tend to glue size the patch and adjust the fit (again) before gluing it in.  It's possibly "mentioned in passing" as many do so.

 

 

Thanks for the responses everyone. 

I got to see Joe and Sigrun's work on a Strad cello auctioned some years ago. Stange how there's so much jaw dropping skill and work linked to the Weisshaar and Shar Fine instruments shops .

[The Violin Beautiful]

I always glue size a patch before gluing it in. The unsized endgrain soaks up so much that it can starve the joint. It’s not necessarily that an unsized patch wouldn’t work, just that I think it would be harder to be certain that the bond was strong throughout. I see the sizing as added security and a chance to double check the fit once moisture has been added to the patch.