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Materials:
Gorgeous tin ceiling panels make great moulds and are available
from:
Brian Greer Tin Ceilings
1572 Mannheim Road, RR2
Petersburg, ON, Canada, N0B 2H0
(519) 743-9710
(519) 570-1447
Specifically you'll need:
- Tin background or 'filler' ceiling panel for the mould - Filler
#101A
- Tin cherub face with wings - Specialty Item #308
- Tin trim pieces for the edges -
- Moulding or Cornice #202
- Cement or grout colourant
- Grout sealant
- Liquid soap
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Tools
- Tin snips
- Duct tape
- Drill and drill bits
- Rubber mallet
- Rubber pail
- Long rubber gloves
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Steps:
Use a drill bit to start a hole in the centre |
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Decorative tin panels really make fantastic moulds. Master
tinsmith Brian Greer provides a staggering assortment of patterns
that will give you brilliant design options.
I used Brian's cherub for the centre of my mould, surrounded
by stippled filler. I also used 2½" trim for the
edges, and duct-taped it into a 20" x 11" rectangular
mould.
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Then use tinsnips to cut out the centre section |
Right and left handed tin snips for cutting curved lines |
Best tin snips for cutting straight lines |
| Draw a rectangle on the stippled background material, leaving
the border a bit deeper at the bottom because that is where
we'll put a candle. (Also, Leonardo da Vinci discovered that
the human eye sees the centre of an object just above the actual
centre, so it's more pleasing to the eye to leave about half
an inch more at the bottom compared to the top.) |
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The cherub should fit nicely inside the stippled background
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Cut the outside corners to fit snuggly |
Tape the pieces together on the outside surface of the box |
Tape the sides to the bottom |
Tape the outside corners firmly together |
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| Once you've taped your box together with duct tape, add a
wire votive-holder by punching a hole in the mould two or three
inches below the cherub's face. Pass an 18" piece of 12
gauge copper wire through the hole. Make a four inch loop of
wire inside the box so that it will be firmly embedded in plaster.
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Use liquid soap as a release agent |
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| Next, coat the inside of the mould (but not the copper wire!)
with liquid soap, which allows the plaster to release easily
after it's hardened. For a "sanded" finish on your
cherub, sprinkle a layer of sand over the soap. A bit of warning;
It's difficult to keep the sand in place when pouring the plaster.
It tends to wash away from the pour location. If you solve this
little irritation, please let us know how you did it! |
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Put the mould in a sand box and support the sides |
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| The tin is quite flexible so it's a good idea to have a cardboard
box filled with sand standing by. Sand in the bottom of the
support box will hold the uneven surface of the face of the
cherub. Use wooden blocks along the sides to prevent the walls
of your mould from blowing out with the twenty to thirty pounds
of plaster they'll be holding. |
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Don't use lumpy plaster - it should be silky, like flour |
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Plaster can be ruined by humidity and time, so select your
plaster with care. Usually, there is a manufacturers date
stamped on the bag and it shouldn't be more than six months
old. If it has hard lumps in it, don't waste your time trying
to use it because it will just turn into big uncooperative
clumps. Good plaster should have the texture of finely milled
flour.
Mix Mastery
The plaster-to-water ratio is about two pounds of plaster
to one pint of water.
To find the amount of plaster you need, multiply the dimensions
of your form - width x length x depth. This will give you
the total number of cubic inches inside your form. Divide
this number by 30. That's how many pounds of plaster you need.
(But have a bit extra just in case.) For this project, you'll
need roughly 16 pounds of plaster.
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Make some colour samples |
Mix the colourant into the water first |
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Measure 8 pints of water into a tub and pre-weigh the plaster.
If you're using a colourant, mix it into the water before
adding plaster. Dry cement colourant seems to work best.
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Always add the plaster to the water sifting it through your
hands |
Mix the plaster from below with your hands |
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| Now, take one handful of the plaster and sift it through your
gloved hands into the tub of water. Keep sifting plaster into
the water by the handful (it takes a while) until it naturally
builds up like a little island in the centre. Let it 'slake'
(just sit and absorb water) for about three minutes. Then mix
the powder into the water with your fingers, coming from underneath
like you're tickling the belly of the island. Go slowly or you'll
whip bubbles into the mixture and your cherub will look like
a smallpox victim. |
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It is ready to pour when a wake is left after drawing your finger
across the top |
Pour the plaster down a stick to reduce bubbles |
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| The plaster is ready to pour when you can run your finger
along the surface and the mixture forms a soft trough.
Pour the plaster into the mould slowly and gently. Letting
it flow down a vertical stick helps to prevent bubbles, but
you'll still have some, so once all the plaster has been poured,
release bubbles by tapping on the bottom of the mould with
a hammer or rubber mallet.
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While the plaster is wet, insert a copper wire hanger |
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| Insert a copper hanging wire into the plaster from
the back so that it can be hung on the wall later. |
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Peel the form away from the plaster
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Clean up any lines left by the mould while plaster is still
soft |
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| As the plaster cures, it will become quite warm. After two
or three hours it will cool somewhat and is then ready to be
removed from the mould. Cut away the tape at the corners and
around the wire at the front and the mould should just fall
away from the plaster. At this stage the plaster is called "green"
- it's soft and workable. So if there are any unwanted ridges
or marks left by the mould, now is the time to remove them with
a Popsicle stick or screwdriver tip. You can also fill any unwanted
bubble holes with some freshly mixed plaster. |
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Seal with several coats of grout sealer after thoroughly cured |
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| The plaster will continue to set for two or more weeks, depending
on humidity. It can be cured more quickly by placing it in a
warm, 250-degree Fahrenheit oven for a few hours.
Once the plaster is fully cured it should be sealed with
grout sealer.
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Finished plaster with candle |
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| If you really get into plaster, one of the best books on mould
making is called, "Mold Making, Casting & Patina"
by Bruner Felton Barrie and is published by Adams,
Barrie Felton and Scott Publishing, Box 247, Princeton, NJ 08540
Have fun with plaster and don't get frustrated if it doesn't
come out just right the first time. Even Leonardo da Vinci
got frustrated, which is probably why he was once heard exclaiming:
"Why does the eye see a thing more clearly in dreams
than the imagination when awake?"
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Artisans'
work featured on this episode:
(click pics for Artist info and larger
images)
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