Here is another experiment.
Undercut was always a problem in most plastic bottle.But if you are willing to sacrifice a mold in our case the bottle than shapes will exciting for the cast. Here I used Genteel washing powder bottle as a mold base and old lamp I found in the house somewhere.
Step 1: Prepare the Bottle and Lamp
wash it rinse it dry it.
Step 2: Hole in the Bottle
Here I didn’t wanted to make a big hole in the bottle bottom to let wire out so I cut the wire from center and then passed the wire through.
Step 3: Secure the Cables on the Top
Secure the cables on the top so doesn’t hinder while pouring the cement mixture.
Step 5: Casting
Secure the lamp base in the center .make sure it doesn’t move during initial hours after poring the cement mixture.
After a day or two take the cutter and chop off all the plastic bottle.Planning how to cut out the bottle will actually help and make task much easier.
Step 6: Breaking the Shell
One of the most fun activity of this build.
Plan the cut lines and plan so its easier to remove the shell.