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Nick Allen

Glue absorption in purfling channel endgrain...

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7 hours ago, Don Noon said:

 but I also have been considering trying the blasphemous idea of using non-foaming polyurethane glue to (hopefully) avoid all of those problems. And create different ones.

27 minutes ago, scordatura said:

Egads. That is tantamount to lutherie heresy! :lol:

Is fish glue also heresy?  Maybe not as bad.

But it seems to me that this modern glue might solve all of my concerns:  it doesn't have water so it won't expand the wood, it's thick so it won't wick into the grain, and it has a relatively long working time.  I don't know if it brings any downsides with it (other than purists finding out you use it), so I'd have to test it first.  It's not like purfing is a joint you have to take apart occasionally; even with hide glue, it's pretty irreversible anyway.

 

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I am one of those who use the glue re-heated at least once or more for purflings, but more than for a precise choice, to avoid wasting it :P (I would not use it for structural gluings anymore). I also use it at 70°/72° to slow down the gel time.

But I think the most important thing is to know the expansion of your materials when glued and understand how much to make the channel wider than the purflings. I use poplar for white and pear for black, which ensure a good swelling (especially poplar) and I need a channel a tenth wider than the purfling to get perfect seams without to much pressure on the sides of the channel. My purflings go in and out of the channel very easily just using the fingers, without giving any sensation of resistance (if pulled in and out gently and correctly). I also use a lot of glue passed over the purfling as well as the glue in the channel, and despite I inlay the purfling with the fluting channel already made I have never had problems from excessive absorption.

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10 minutes ago, Don Noon said:

Is fish glue also heresy?  Maybe not as bad.

But it seems to me that this modern glue might solve all of my concerns:  it doesn't have water so it won't expand the wood, it's thick so it won't wick into the grain, and it has a relatively long working time.  I don't know if it brings any downsides with it (other than purists finding out you use it), so I'd have to test it first.  It's not like purfing is a joint you have to take apart occasionally; even with hide glue, it's pretty irreversible anyway.

 

With synthetic glues my main concern would be the excessive waterproofing effect that could reveal itself just when the ground or the varnish is applied...too late<_<

In addition to eternal damnation for the betrayal of traditions, of course...:D

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If glue stays in the pot for hours on end or is left out at room temperature it will deteriorate although remelted  two or three times should be just fine for medium strength uses like purfling. I find that it is a very good idea to soak the glue, melt it once adding water until thin cream texture. Then I  stick it in the refrigerater and allow it to gel completely and then remelt it again. At that point it will be more liquid than before without any "snottiness"and can be adjusted to whatever fluidity you want and used for very strong joints such as center seams, bass bars or neck sets. It can be refrigerated and remelted a number of times afterwards but will lose a little strength each time. For top glue I will thin it and remelt it quite a few times before use and only discard it if it starts to smell or no longer gels when refrigerated. I am using 315 gram glue from North Carolina for almost everything.

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3 minutes ago, nathan slobodkin said:

If glue stays in the pot for hours on end or is left out at room temperature it will deteriorate although remelted  two or three times should be just fine for medium strength uses like purfling. I find that it is a very good idea to soak the glue, melt it once adding water until thin cream texture. Then I  stick it in the refrigerater and allow it to gel completely and then remelt it again. At that point it will be more liquid than before without any "snottiness"and can be adjusted to whatever fluidity you want and used for very strong joints such as center seams, bass bars or neck sets. It can be refrigerated and remelted a number of times afterwards but will lose a little strength each time. For top glue I will thin it and remelt it quite a few times before use and only discard it if it starts to smell or no longer gels when refrigerated. I am using 315 gram glue from North Carolina for almost everything.

I also keep glue in the refrigerator after it has been dissolved the first time, it works really well.

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Whhat, you pros don't have a festering, gurgling pot of glue constantly heated, to which more granules and water are added as needed, not even really measured? You mean, you always know how many times it's been heated and re-solidified in the fridge? Wild.

:blink:

I think my husband got some of that NC 315 glue as a gift.   He probably mixes it with 225 strength. But the rest of the process is what Nathan described. Is this a Jacques Francais thing? That would make sense.

 

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4 hours ago, Davide Sora said:

With synthetic glues my main concern would be the excessive waterproofing effect that could reveal itself just when the ground or the varnish is applied...too late<_<

In addition to eternal damnation for the betrayal of traditions, of course...:D

I have already earned my prominent spot in the great torrification chamber below for my abuse of wood, VSO's, and consorting with the devil's machinery.  One more demerit won't make any difference.

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On 7/10/2020 at 7:39 AM, Bodacious Cowboy said:

Although I'm aware of "The Hargrave method" I was always concerned that the glue coating on the purfling would melt and stick to the bending iron. Does this not happen? 

Everything is precut and dry fit to make sure it is perfect, then using a needle or sharp knife, the precut perfectly dry fit purfling is removed.Then put up on tiny no-stick dowels to dry after application {I use ballpoint pens over wax paper} To apply the glue I make a strong thick batch and use my bare fingers to slather it on by dipping my thumb, forefinger and middle finger in the hot glue and then I pull the purfling through the junction of my fingers {like a pasta making machine} this coats all 4 sides of the purfling and puts on a nice "squuegy'd" amount on so as to not mis-shapen the purfling by adding to its dimension too much,it will swell, but then return to normal after dry.

The finger slather method allows one to use a thicker stronger glue, yet apply it thin so to not make the purfling too fat via the added glue film

Once the glue is dry, if all goes right, the small amount of added thickness {the layer of glue film} will make it so the purfling fits snugly into the channel and if it goes really well you will need to push and seat it with some "device" {purfling pick, thin stick, blunt tooth pick etc.} 

Any clamping needed for any wayward pieces that do not want to behave should be done prior to water application. With no stick barrier such as wax paper

After everything is set and adjusted {if you are going to need to snug fit with a tool, I suggest getting the miters right first} Then use a ceramic mug with just a quarter inch of water, that way it boils in 15 sec and brush on freshly boiled water, just reheat small amounts of water with the shop microwave and you'll know you've always got insta-glue melting water temp.

When I first heard the concept from Roger,my first concern was that it would not work that good and the purfling would be substandard glued in because of the "suck in factor" so I did several test strips of purfling installed the wet set way and then Rogers way. The act of demolition was about the same difficulty for each 

I have never had any issues with purflng coming out, at ;least that I am aware of.

edit; the brush that you apply the water with should be rinsed clean periodically{every two/three passes} so as to avoid the brush itself picking up too much glue and painting it on the surface

the advantages of this method are great, you have all the time you need to get the purfling right where you want it and perfectly fit, there is no rushed mad glue dash, no syringes,toothpicks,brushes,applicator bottles or whatever way one gets the glue in the channel or on the purfling,

The next advantage is the cleanliness, there is no clean up, no residue,no none of that, this saves time,particularly if you end up with what OP has and you really don't want it and try to remove it, it really turns it into a very relaxed easy operation as compared to installing it any other wet set way.

 

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4 hours ago, jezzupe said:

Everything is precut and dry fit to make sure it is perfect, then using a needle or sharp knife, the precut perfectly dry fit purfling is removed.Then put up on tiny no-stick dowels to dry after application {I use ballpoint pens over wax paper} To apply the glue I make a strong thick batch and use my bare fingers to slather it on by dipping my thumb, forefinger and middle finger in the hot glue and then I pull the purfling through the junction of my fingers {like a pasta making machine} this coats all 4 sides of the purfling and puts on a nice "squuegy'd" amount on so as to not mis-shapen the purfling by adding to its dimension too much,it will swell, but then return to normal after dry.

The finger slather method allows one to use a thicker stronger glue, yet apply it thin so to not make the purfling too fat via the added glue film

Once the glue is dry, if all goes right, the small amount of added thickness {the layer of glue film} will make it so the purfling fits snugly into the channel and if it goes really well you will need to push and seat it with some "device" {purfling pick, thin stick, blunt tooth pick etc.} 

Any clamping needed for any wayward pieces that do not want to behave should be done prior to water application. With no stick or no stick barrier such as wax paper

After everything is set and adjusted {if you are going to need to snug fit with a tool, I suggest getting the miters right first} Then use a ceramic mug with just a quarter inch of water, that way it boils in 15 sec and brush on freshly boiled water, just reheat small amounts of water with the shop microwave and you'll know you've always got insta-glue melting water temp.

When I first heard the concept from Roger,my first concern was that it would not work that good and the purfling would be substandard glued in because of the "suck in factor" so I did several test strips of purfling installed the wet set way and then Rogers way. The act of demolition was about the same difficulty for each 

I have never had any issues with purflng coming out, at ;least that I am aware of.

 

Thanks, Jezzupe, that makes sense.

My concerns about sticking to the bending iron arose from RH's Bass book, where (I think) he mentions applying the glue to the outside during the purfling making process,  before bending and fitting. I'm sure your way would work, though.

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On July 10, 2020 at 9:26 PM, not telling said:

Whhat, you pros don't have a festering, gurgling pot of glue constantly heated, to which more granules and water are added as needed, not even really measured? You mean, you always know how many times it's been heated and re-solidified in the fridge? Wild.

:blink:

I think my husband got some of that NC 315 glue as a gift.   He probably mixes it with 225 strength. But the rest of the process is what Nathan described. Is this a Jacques Francais thing? That would make sense.

 

I think I figured this out myself actually. The gelling and remelting basically makes it act thinner even though you are not adding more water. After that first time however the glue tends to thicken slightly with each remelting which requires  adding water which dilutes and weakens the glue. If I remember at Jacques' we were often sharing glue pots and it was sometimes difficult to know just what was in them.

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