Vacuum Gauge

Vacuum Gauge
Vacuum Gauge

0-30Hg (mercury) vacuum gauge.

885-5 Vacuum Gauge, 1 ea.

Vacuum Bagging Techniques (pdf)







The Purpose of the Vacuum Gauge

The vacuum gauge shows how much vacuum you have pulled on the part. Vacuum-bagged parts should have at least 10″ of Hg of pressure acting on them to properly consolidate the part.

The Gauge screws into a vacuum cup and is placed over a ½” “X” cut in the vacuum bag film. Vacuum measurement is expressed in inches of mercury (0-30 Hg). Each increase of 1 inch of mercury (a single increment on the gauge) indicates an addition of about seventy pounds of pressure per sq ft (.48 psi) at sea level.

Advantages of Vacuum Bagging

All of the layers of fabrics and other materials used to fill the repair area can be wet out and applied at one time.

No matter the weight of the material or the location of the repair, the vacuum film will hold materials where placed.

The last layer of glass laminate can be laid up dry (not to exceed 25% of the glass laminate total). The vacuum generated pressure will force epoxy into the laminate, thereby reducing the amount of epoxy drawn into the breather fabric.

The higher clamping pressure results in a lower resin to higher fabric ratio and in a much stronger repair laminate for any given thickness.

After the initial cure stage (about 20 to 30 minutes at room temperature), the cure rate can be accelerated by warming the laminate with a hair dryer. Using this method, the entire cure time can be reduced by more than half.

When the Release Fabric is stripped from the cured repair, the excess epoxy is carried away in the breather fabric. The waxy surface film (amine blush) that may form on the surface of  some fully cured epoxies is also carried away. This eliminates the need to wash and dry the surface before proceeding with the finishing processes.

For more information on vacuum bagging epoxy laminates, read Rachael Geerts’s Vacuum Bagging Basics at