Last week I did my first plaster crown mould. I didn't want it, mind you, but the alternatives were too costly or too time consuming. It seemed like a simple enough thing to do. It was a 8"R outside curve. A small job. I made a template out of a cheap trowel. I used plaster of paris. I applied it to the corner and made a strike. 30 minutes later I did the same thing again, building it up to the height I needed. The final product was disappointing. I could never get a really smooth surface in the plaster even through I was thinning it as much I could. When it dried, I had to spend a couple hours filing and sanding trying to get an acceptable job. Plaster of paris does not sand well. Did I use the wrong product? What is the secret? I saw them do it on "This Old House" about 6 months ago and I did what they did as best I can remember. Thanks for your expertise.

 

I'm going to move your thread into the Patching and plastering forum of the website.

 

Hi
Doing plaster crown molding is hard to do.
you cant buy experience you have to earn it.
Professional plaster go to trade school to learn it.
It's not something you can learn overnite.
On this old house they have pro not diy people.
Check your location if they offer plaster course as hobby.
Good luck thats why i used the fiber type crown less expensive as wood.

cheers

pg

 

pg said a mouthful in that post and very true too! But if you've got the time and patience, you can usually eventually reach acceptable results. Personally I go with the resin trim pieces myself, alot quicker & cheaper IMO.

Anyway I believe what you should be using is a molding plaster, don't think you'll get acceptable result with the plaster of paris. Lot of guys make a cast or mold of the piece & then pour the plaster into the mold, pure soap like ivory is used on the mold as a release agent. Baking soda can be sprinkled onto the mold as well & after it sets up you wash away the soda off the surface & it will give you a pitted look like natural stone.

Tightcoat & others here with more plaster experience may have more suggestions for you. Good luck & Happy New Year! :glocke:

 

The local Depot store held an instore workshop to show how easy the resin precast product was to use. I bought it for 2 rooms and it flew up with the inside corners and outside corners already to put up. Just straight runs in between and you have a beautiful crown moulding. BTW almost everyone watching the workshop in the store was sold on it. Coping (no pun intended) much better these days now. HAPPY NEW YEAR.
-Bob