What causes acoustic guitar belly bulge?
Sometimes acoustic guitars develop a bit of a belly. Over time the string tension pulls on the bridge, angling it forward and warping the top, which in turn raises the action and causes other structural problems down the line. ... These are heated, put in place on the top and on the bridge plate, then clamped.
How much belly should an acoustic guitar have?
A healthy Martin should have a slight belly. If the top is dead flat that is a sign of a dry guitar. If you lay a straight edge across the top just behind the bridge you should have a gap on either side of the top. If this gap is more than 1/4" on either side you might have over humidified or some structural issue.