There are two problems with guitar tops that I see on a regular basis. One is the bowed up top right behind the bridge. And along with that many time the bridge starts to lift up. The second is a collapse around the sound hole. Both of these issues can be fixed with a little time and patience.
In this article I will tackle the bowed up top issue. Once a guitar starts to have this problem it does nothing but get worse. Once the bridge starts to lift, the pressure of the strings pulling on the bridge just enhances the issue. I have seen guitars where the back edge of the bridge is almost a quarter of an inch off of the top. A lot of times the only thing keeping the bridge from snapping off is if the bridge has a nut and bolt holding it on. In many cases the bridge cracks under the pressure. There is a solution to this issue. You may not get it back one hundred percent but you can get it back to a playable condition.
1. Remove the strings when you notice this happening. The sooner you can do this the better. If you see the bridge lifting get the pressure off the bridge.
2. The main reason guitars get to this condition is lack of hydration. Ideally guitars should have a hydration level between forty five and fifty percent. They need a drink just like us.
Place a damp rag, not soaking wet but really damp, in a plastic container, that will fit inside the sound hole and one that you can place under the bridge. I use large yogurt containers and cut them down. I then use the container plastic cover to cover the sound hole. Just cut a flat edge on the cover.
As well cover the string peg holes on the bridge to keep as much moisture inside the guitar as you can.
3. We now need to apply some pressure to the area that is bowed up. I use sheets of paper folded up and taped together. I start off with two or three of these and place them directly on the hump behind the bridge. You will need enough that when you put the guitar in a hard case and when the case is closed it is applying a mild pressure to the hump. I also used a piece of foam that is also flexible. If you don’t have a guitar case then use something not too heavy and place it on top of the folded paper.
4. Patience! After five or six days add another layer of folded paper. Do this for four weeks. Check the rag to make sure it is still damp each time. I normally have to dampen it twice in a four week period.
Over this time you will notice that the hump has gone down and the bridge has lowered. If you are real lucky over this time it will completely flatten, but most times there will still be a small hump.
5. Since you have lots of time you can order a JDL Bridge Doctor. If you do not use this eventually the bridge will lift more until it will more than likely return to it’s unplayable condition with a badly lifted bridge.
The Bridge Doctor will keep the top and bridge in the position of the amount of repair that was done to it. In other words if you get ninety percent of that bow to lay down the bridge doctor will keep it in that position. It won’t take the hump out by itself. You need to do that with the steps I described above.
I have used this method on a number of guitars and all are still playable and pretty much the same as I fixed them. Hydration is very important in keeping instruments in great condition. It’s always a good idea to have a humidifier in your case or at least one in your guitar sound hole if you keep it out on display.