Often, we find that a repair or restoration involves replacing a piece of missing
plastic. The pictures on the left are of a 60 year old piece of radio gear with just such
After trying several materials, we stumbled upon a product called Plast-Aid
(www.plast-aid.com), typically used for repairing pool and spa PVC breaks.
Plast-Aid comes in two parts, a white powder and a clear liquid. Once mixed
together, it turns into a liquid about the consistency and color of Karo syrup that
can be poured into a mould to create a casting. In about ten minutes, the liquid
turns to a putty that can be shaped. In about another ten minutes, the putty
hardens into a solid plastic that can be filed and drilled.
The subject of the repair on the left was a National Radio Company audio filter. Its
case was made of Bakelite. As you can see, it was missing one entire corner. To
replicate the missing corner, we used a good corner to create a mould that would be
used to repair the missing corner. The mould was made by pouring melted candle
wax into the undamaged corner. Once the wax hardened, we removed it from the
good corner and used painter's tape to fasten it to the missing corner. A small batch
of Plast-Aid was mixed, and a few drops of black acrylic paint were added to color
match it to the case's original black Bakelite.
After the Plast-Aid turned from its liquid to its putty state, we shaped the rounded
corner to the correct radius. In about 10 minutes, the repaired corner was hard
enough for final sanding and painting.
Click on any picture to enlarge it
The missing corner.
Wax mould hardening in a good corner.
The mould, now moved to the missing
The completed restoration, after
painting and reassembly.