Rosette purfling problem

[Mike Crabbe]

I'm sure this has come up, but couldn't find anything in the library:

I was installing a wood rosette ring surrounded by 3 purfling lines on the inside and outside. While I thought I had enough space in the dry fit, when I glued it up (LMI instrument glue), I ran out of space with the outermost line; I could only get about 3/4 of it in so I pulled out what I could. Unfortunately, the glue was setting up and I couldn't get about 2" of the circumference out. It's about .025" thick.

I was considering finding the center (now slightly off center from the original hole due to running out of space) and cutting out and replacing the outermost purfling ring. Dremel might be too wide, so I was thinking popsicle stick method, but not sure about cutting through the hardened glue, etc.

Ideas? Anyone successfully solved this one?

Mike

[Alan Carruth]

This is a pretty common problem. The water in the glue makes the wood swell, and stuff that went in fine suddenly won't go. One of the things you learn over time is just how tight (or loose) to make things so they'e come out right. The alternative is to cut things tight, put the lines in dry, and wick in thin CA.

Scrape as much of the excess glue off the surface as you can, and use the popsicle stick method to enlarge the groove. You may have to put in an extra line.

Alan Carruth / Luthier

[Ron Belanger]

I used to put everything in in one go, but always had fit problems. Now I fit the largest element first, then route channels for the purfling. I give the channels a good coat of shellac and then use medium CA to glue them in. Works for me.

[Chuck Tweedy]

To pile on - but make it more clear.
The best way to install a thin rosete material that covers a wide center ring in the pattern is to:
- NEVER cut out the soundhole until the rosette is complete
- Install that ring in a trough that is custom-cut for the ring (AKA - shallow and just wide enough
- Clamp that ring down well because thin wood veneers will warp like crazy when in contact with glue
- After this is dry, cut the troughs for the surrounding lines/purfling - Cut into the inner ring a bit to get a super clean line.

[Mike Crabbe]

Thanks folks - good advice for next time. I managed to fix this one OK and used CA - much better...
Mike

[Ron Belanger]

Exactly, thanks for the clarity Chuck. Sometimes I tend to be a bit fuzzy

[Mike Crabbe]

Ron - I understood you, except about the shellac. Are you saying you shellac the inside of the channels before putting the purfling in? What does the shellac do for you?
Mike

[Waddy Thomson]

CA will stain the top in the end grain of the channel, so it needs to be sealed with shellac to prevent that from happening. It will not hurt the adhesion of the CA.

[Chuck Tweedy]

Speaking for Ron ... The shellac acts as a sealant, keeping the glue and/or color from the lines from wicking into the top's end-grain.
It is essential when using thin CA because the CA will make an un-repairable stain in softwoods where it has wicked in.
Even worse is when using dark, resinous woods like cocobolo in the rosette. CA liberates the color from these woods, and caries that color right into the softwood grain. Really bad look.
This is much less of a problem when using water based glues, but sealing the channel does help it retain its shape (and firmness) when wet.

Fear not, glues stick well enough to shellac to keep your rosette in-place.

[Ron Belanger]

Thanks Chuck, couldn't have said it better meself.

[Chuck Tweedy]

Didn't see it before, but it looks like Waddy & I posted at about the same time.

Ron, I'll be glad to continue posting on your behalf - IF you come to the next GAL Convention.

[Waddy Thomson]

You gave much better detail than I did, Chuck!

[Joel Nowland]

Mike

Rather than gluing everything in at the same time I glue just the inside and outside purfling first and then add the center inlay after.

I use clothes pins up-side-down using the spring action pressure of the clothes pin handle to hold the purfling inplace as the glue dries.

See photo.

I even use a similar technique for the small ring around the main rosette(not shown) using some knife edge spring clamps I made from 3/8" square 7075 aluminum.

Works great and allows a lot of flexibilty and creativity in designing the center rosette section

Works great!

Joel

[Mattia Valente]

I'm with Chuck and co - it's much, much easier to route for the main wood ring (no need to be super precise or tight), glue it in, and then route channels for the purfling lines. Makes installation a snap.

[Tyko Runesson]

I just don´t get it why you couldn´t take all the binding out when you realized that it didn´t work? Just heat it a short time with an iron and it will easily melt the glueline. Then you could have cleaned all out and and start over again.