I cast my first portal and brick retaining wall. both are about 1/2" too high for where I want to put them.
Use an Atlas miter saw dipped in water and a straight edge until you get it started. The water is to control the dust. Make your cut from the good side. At some point you should be able to snap the piece off and then wet sand the area to level it and control the dust also
Plaster really dulls knife and saw blades so if you might want to use your oldest saw for this purpose.
Dave Nelson
Uas a hacksaw with an old junk blade.
BOB H Clarion, PA
SpaceMouse,
If your plaster has completely dried (week or so) it may be very brittle. To help stop unwanted chipping and make cutting easier, wet or soak the portal and let air dry until scratching the backside with a hobby knife will score easily. When ready cut with a razor saw or best with a small band saw. Plaster of Paris is fairly hard and brittle, next time try using Hydrocal or the W/S plaster for casting. I don’t know what part of the portal you are cutting that is 1/2" too high-bottom or top. If you cut any from the bottom make sure you still maintain adequate clearance. If your portal is on a curve, it may not be wide enough for equipment side clearance. I found out the hard way on both counts. Wouldn’t want you to go there too.
Bob K.
If it’s only 1/2" too tall, a coarse file might also do you OK. You might also try a drywall “shaver” (Not sure of the name - it’s just a piece of wood with a piece of wire mesh wrapped around it).
Rob
The hacksaw worked just fine. Thanks guys.