We would like to show you our newest products - its all about vacuum bagging as described in Andrea Ortona's article in the March edition of theStrad magazine. When we attended Andrea's course in Cremona last June we got very excited of the shown possibilities.
Just imagine making a high precision plaster cast in little more than half an hour - and now think of how much time it usually takes YOU to make a plaster cast.
Let's start:
1) Take your violin top.
2) Put it on its support in a polythene layflat tube that was sealed on one end with a heat sealer
3) Align your white breather fabrics that prevents trapping of air in the bag
4) Make a hole in the bag on one side with a punch to be able to insert the valve
5) Insert the valve
4) Close the bag at the open end with an extruded bag closure
5) Attach the hose (which is connected to the vaccuum pump) to the valve
6) Switch on the vaccuum pump
7) Put the polyethilene in place
8) Put the counterform in place
9) Pour the prepared plaster and add a wooden stabilizing board
10) Wait for the plaster to settle
Enjoy your perfect cast!!!
Trade Secrets: Making plaster casts using vacuum bagging
By Andrea Ortona Violin maker and restorer based in London
A few years ago, an engineer friend took me to visit Renault’s Formula 1 racing car factory. I was amazed by the technology on display: I saw a 3D laser printer creating the design for a car part right in front of me. Then there was the simplicity of a vacuum bag containing part of the car chassis. Vacuum bagging is also commonly used in the veneer industry and in making composite musical instruments.
After this visit, it occurred to me that vacuum bagging could also be used in making casts of violin plates that would have excellent definition, and that it could also open new and safer possibilities in restoration, for example in the shaping and gluing of patches, arching corrections and hot sandbag sessions. Nowadays it is common practice to use plaster casts in the course of various restoration procedures to support plates and other parts, thereby preserving their original shape. Plaster-cast copies of originals can also be used as documents for reference.
Making violin plate plaster casts using vacuum bagging is quicker than traditional methods and has many advantages over them. It avoids the need to glue the original to a support and does away with the difficulties involved in using oil to make the protective layer adhere. Air bubbles between the plates and the protective layer are eliminated, as is the danger of lowering the arch when there is air suction from below.
With vacuum bagging it is also possible to produce precise casts of the inside of the plates, hollow and bare wood areas. Making casts of these areas using traditional techniques is very difficult, if not impossible. Vacuum bagging also overcomes problems with wood distortion where thin plates are involved. With some imagination there are many uses for this technique.
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