Tag Archives: lainvencible

Restoration photos III

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A friend wanted to hear more about Vicente Arias and I realized that I never finished telling the story of its restoration. Carrying on from where I left off:

From looking inside the un-opened guitar, I had assumed that the hidden linings would be the same as the visible ones: continuous cedar. However when removing the binding I could see that they were individual spruce glue blocks. When I made a copy of this guitar (years before ever opening it) I put continuous reinforcements both visible inside the guitar as well as outside the inner back and inside the outer back. It was a struggle to see how to completely immobilize the inner back and I opted to glue in cut sections of reinforcement. Well, as always, this 19th century builder had a better idea than mine. He made the interior back even smaller than necessary and then glued triangular blocks wedged between it and the sides. These wedge glued to the sides provide the glueing surface for the outer back, the spanish peon. The inner back is imobilized so that we don’t have unwanted vibration and with some preparation we have the perfect surface to glue the outer back to. Now it is also clear that it was not such a bad idea to make a saw cut to remove the back since the triangular blocks are more delicate especially if they are separated from each other as is the case here. Between the cut of the saw and my spatula some glue blocks were damaged and had to be replaced. Then, to give a slight curve to the back, the height of the blocks had to be increased so that we could plane or sand them to receive the back. The profile of the sides has to rise a little at the waist of the guitar. I did this by sanding the rim to level the repaired blocks and then gluing a spruce back on top to get the height lost by the cuts and repairs. This allowed me to use the plane to get the contour I need for a healthy domed back. After planing I was able to cut away the interior spruce leaving only a rim of spruces just thick enough to correct the curves.

The bars are now curved but a little less than in a new guitar, counting on the probability that the back does not continue to lose width as it ages. The only thing that remains it to couple the back and glue it, prepare the channel for the bindings, prepare the borders with the black and white fillet and glue them too. We chose to leave the green fillet intact on the guitar due to the difficulty of finding or making the same green. The last step is always to re-polish the guitar which in this case was a bigger job than for most restorations.

640 scale

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My short scale guitars have always sold quickly and have made their owners very happy. Here is a recent one which sounds great and is of course easy to play. This one uses the body shape and bracing that Rolf Eichinger used on most of his later instruments. I think I might keep this “plantilla” for all of my short scale instruments.

Using hide glue

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I got some feedback from the latest video I posted and it gave me the idea to explain how I use hide glue. I may have already written something about this and certainly many others have done so but as we are all sitting at home anyway waiting out this worldwide sickness I guess it won’t matter if I have covered some of this ground already. I love hide glue. It has fast grab, the glue lines are often invisible, and in the case of rosettes I think it heats up again upon installation and resettles into the perfect round shape. Hide glue doesn’t creep, I think it is less damping than other glues and clean-up, working the joint and re-glueing are easier. Heat resistance is very high and it doesn’t show up like PVA under a finish.

There are a few things to keep in mind when you use hide glue:

1. You need to make perfect joints especially with thin stock. The glue shrinks as it loses water and draws the two pieces together and causes deformations where the surfaces are not perfectly mated. With thicker stock the result is a weak joint because hide glue won’t fill up the space and even if it does it won’t have the same strength as a very thin glue line. A thick glue line or pockets with some glue inside has another drawback: They might attract moisture and thereby mould or insects. It will not fill in gaps.

Guitar International magazine 1989

2. The glue needs to be warm (liquid) at the time of applying pressure. This often means preheating one or both pieces or heating once they are fit together in the case of thin pieces. I heat bindings, back fitting (like in the video yesterday), rosettes, and plate joints after applying the glue and joining the pieces. Almost every other operation involves heating the wood beforehand. One exception I can think of right now are the peones (triangular glue blocks) which seem to stick well enough just from the heat in the glue. I preheat with bridges, fretboards, bars and fan braces, headplates, neck stock; I even have a heat blanket for heating when I glue up a large number of veneers at the same time. Flame is the traditional way to heat the glue joint after the fact. I have seen it used on rosette installation and glueing on the back and when glueing the two halves of the back together. Of course you can use other methods but I love these traditions and it really works well. One of the advantages is that it seems to dry out the wood a bit less than something like a heat gun.

3. You have to learn to get the consistency right and each job requires a specific consistency. When you are heating up after the fact a slightly thicker mix can be good so that the glue flows less before the heat is applied. Bridges and fretboards like a more liquid mix because ebony and rosewood won’t absorb so much of the glue and a glue line which is too thick could fail. Another theory that I have is that although a thick mix has less water per unit of glue a thinner glue has less total water going into the wood (bridge and fretboard don’t like water). I like a very thin glue too for installing a rosette from its components because it wicks better. In general you can use glue thinner than what you are used to and it will work better.

4. Reversiblity is nowhere near as easy as some will try to tell you. If you can break the joint (usually because of a thick glue line) you can do whatever you came to do and it will re-glue very nicely but opening a tight joint with very little glue (the best kind) requires so much water and heat that you often severely compromise the wood. On a partially open joint that needs repairing this is much easier because you can get the heat and water in more easily.

5. You need to plan ahead to have it in its gelled state and heat it up when you need it.

Glueing the back on

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You might want to turn the sound right down on this one.

Torres 640 extra fret

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The original SE153 is 650 and of course only has 19 frets. Although I have made many with rosewood, this is the first time I have changed anything else on this model. The measurement at the nut is 50 on this one and on all of the SE 153 copies I make. 640 works very well because of the small body while the extra fret is seen by some to be indispensable for modern music. I have resisted making the extra fret standard just like I don’t usually put a marker on the 7th position but obviously these things can be included for no extra cost at the time of ordering.