Taking a mould of a cornice up on the ceiling

Hi All,
Great website... I'm very new to this so here we go. How does one get in contact with a member as i have read the response by "the noup" in regards to the above subject & was wondering if he could explain it with diagrams as i just don't get it. Being that once you put plasticine over the plaster cornice & then i believe pour the silicane how does the silicon get into all those detailed corners if the plasticine is already there? I'm confussed i have never done this before & would appreciate some help as i'm trying to make a duplicate of a very old plaster corince up on the ceiling. Thta's the other problem how does one make a copy whilst the orginal is still stuck on the ceiling?? Would greatly appreciate any assistance. Thank you
Will

Hello Wil, welcome to the forum

You can get in touch with a member by clicking on his profile page and there is the possibility to send him a PM

Also, at the message he placed you can click underneath his avatar on the icon of a little envelope which says 'send me a private message' if you put your cursor over it.

Let me know if you succeeded please

Thanks for that much appreciate it.

If this model is up in the air (inverted or vertical), then that manner of mold making will be extremely challenging to accomplish.

Unless you can get the model down to floor level & work on a bench, you should consider making a silicone mold using a 'brush-on' technique where you apply the rubber & build 'out'. Many modern materials (silicone included) are available for such an application. But keep in mind that the rubber mold is only one component of the overall mold; when that rubber has cured fully, then you will need to apply a support shell to the exterior of the rubber in order to help the rubber maintain dimensional support - otherwise without this support shell the mold will be like a rubber glove & will just flop & certainly distort when you cast it to make your reproductions.

In silicone choices I have used two different materials for this application: REBOUND 25 & MOLD MAX STROKE; both are 2-part brushable materials that need to be mixed & applied in layers - usually about 5 coats to build rubber thickness to 3/8" thick then left to cure. There is an additive called THI-VEX II which can be added into isolated batches of rubber to fill in undercuts or deep pockets. The rubber can be pigmented so you can see your coverage applications...

For mothermolds (or support shells), PLAST-PASTE trowelable urethane plastic is great. It is lightweight & strong & only needs to be about 1/2" thick - as opposed to plaster w/ burlap.

Attached is an image I was involved in making molds of ancient Guatemalan pillars which are housed at the Museum of Man at Balboa Park in San Diego, CA.