Purfling Bending?

[Gordon Bellerose]

There is a thread below in which the poster asks about bending rosewood binding, and I read that completely.
It did not address bending purfling, and that is my question.

Does purfling have to be bent like binding? It is quite thin and wide for that, isn't it?

[Michael Lewis]

Well, that depends on the size and shape of your material. If you mean purfling like herring bone then yes, you have to pre bend it. If you are making parallel lines (BWBW> > > etc.) you can just put them in place and glue them as they are quite flexible.

[Tom West]

Gordon: For purfling on the sides I glue them to the bindings. Tape the strips together with the purfling back to back and bend in the bender. For the top, such as herringbone, they are run under hot water, and bent around a flat form, coaxed into shape with a hair dryer, then held in place with a thin caul and finish nails and left to dry. These are then installed at time of binding.
Tom

[Gordon Bellerose]

Actually that does answer my question Tom.

Michael:
I have done multi-strip plastic binding before, so that wasn't a concern. The herringbone, or other type of decorative purfling was the direction I was going.
Thanks to both of you for responding so quickly.

[Trevor Gore]

Purflings made up of lots of bits (e.g. herringbone) are prone to falling apart if they get too wet (or wet at all). Suppose you want to use herringbone on a Venetian cutaway: A trick that works for herring bone is to warm it length-wise on the part that will end up between the butt side of the waist and the neck, going around the cutaway. Then, with a blunt knife, separate the herringbone down the "spine", leaving that end of the purfling strip split more-or-less down the middle. Be careful not to loose any "bones" out of the side that doesn't have the "spine" veneer attached. At the right temperature (quite cool), this splitting goes very easily. Then bend the purfling to fit the top edge in the normal way. Because each part of the length with the tight bends is now only half as wide (approx) it is only 12% as stiff (cube rule), so much easier to bend. I do it dry. I usually glue on all the purfling and binding together at the same time. The split purfling just glues back together as you tape it on with the binding. Rosettes can be done in a similar way, if you need to.

A couple of pics:

[Gordon Bellerose]

Trevor,
I see by the pictures what you are saying. The split down the center allows each "side" to move somewhat independently around the corners.
I am assuming that by the time you get around a corner, the strip would naturally compress back to normal.
In the bottom picture, it does seem as though the split could carry on for a while.

Do you use some heat when bending?

[Trevor Gore]

The split down the center allows each "side" to move somewhat independently around the corners.

That's correct.

I am assuming that by the time you get around a corner, the strip would naturally compress back to normal.

Around a Venetian cutaway, there's the double curve; around the "horn" then into the cutaway, which reverses the curvature, so the inner and out part of the strip have very similar path lengths. A bit of glue between the two parts as they are pulled together by the tape when the bindings are glued on (simultaneously) makes sure that the two parts of the purling glue themselves back together.

In the bottom picture, it does seem as though the split could carry on for a while.

I go from neck end of the purfling strip right to the lower end of the waist curve. About 320mm or so.

Do you use some heat when bending?

Yes; dry and it doesn't need much heat.

[Gordon Bellerose]

Thanks Trevor.
That is really good information.

I do have one more question. Our discussion has centered around herringbone purfling.
Does this change if a different type of purfling is used? Say for instance a chevron, or other pattern like the walnut maple rope in the link below? There is no obvious center line on that type.

http://www.grizzly.com/products/Purflin ... Rope/T1127

[Trevor Gore]

I do have one more question. Our discussion has centered around herringbone purfling.
Does this change if a different type of purfling is used? Say for instance a chevron, or other pattern like the walnut maple rope in the link below?

This is where you need properly made purfling. Not that the Grizzly stuff isn't; I don't know.

When I did this guitar...

...the rope binding was made with sacrificial outside layers glued on with a heat resistant glue. The segments are glued with low temp glue. When bent to shape you get shearing on the parallelogram interfaces without the segments falling out. When cool, they re-glue themselves. Extra purfling lines can be added as desired, but when all are glued in, the outside sacrificial layer is scraped back to reveal the rope, with the inside sacrificial layer becoming a purfling line.

Here's a closer pic...

[Gordon Bellerose]

[quote][This is where you need properly made purfling. Not that the Grizzly stuff isn't; I don't know.][quote]


Thanks for all the help Trevor! I hope lots of people are reading this.
I'm not necessarily buying purflings from Grizzly, it was simply a link to a visual of a different kind of purfling. But if someone were to recommend them, I'm certainly not against it.

It would be a shame to go through all the effort and have an inferior product deliver a bad result, as with so many things in luthiery.
On that topic, where can high quality purflings be purchased? Remember, I'm in Canada.

There is a couple of local places I can buy, but how do you tell if it is good, or not?

[Barry Daniels]

How can you tell if it is good? Either through recommendation of a trusted source, or personal experience.

[Bob Gramann]

Most purfling isn't so expensive that a purchase for testing is prohibitive.

[Gordon Bellerose]

I agree Barry.
Never having used ANY purfling other than the multi-strip plastic you taught me how to do, I have no idea what to look for.

Thanks Bob.
I will just have to try some and see how it goes.

[Barry Daniels]

If you stick with purling from the regular luthier suppliers you will be good. Stuff from general woodworking suppliers is a bit iffy.

[Nate Scott]

...the rope binding was made with sacrificial outside layers glued on with a heat resistant glue. The segments are glued with low temp glue.

Great tip. What glue are you using for the sacrificial layer?

[Trevor Gore]

Great tip. What glue are you using for the sacrificial layer?

Urea formaldehyde.

Tony Francis (New Zealand) made the very nice stuff in the pics above.

Thread on how he does it here.

[Tom West]

Purflings made up of lots of bits (e.g. herringbone) are prone to falling apart if they get too wet (or wet at all).

Trevor: Have heard this said many times by different folks but have not found it to be true. Every piece of herringbone I have ever installed was run under hot water for a minute or two before bending. Been doing it for a looooong time and have not had one piece of herringbone that there was even an indication of it coming apart. All my herringbone has come from LMI, so maybe that speaks to the quality of the product.
Tom

[Trevor Gore]

Clearly, not all purfling is created equal! The last batch I had would fall apart if it clouded over!