Casting of detailed pieces using the wet water and pipette technique:
When you want to cast detailed pieces out of plaster it is most likely that you will not get good results when you cast these items as you normally do
when casting normal building blocks. Fortunately there is a technique that makes it possible to get detailed casts from tiny detailed ornaments and such.
With the write approach and the right tools it is actually very simple.
In this example I will use my shield / skull mold. This mold has only got small detailed pieces in them that most likely will cause lots of problems when
you cast them. All the pieces within the mold are originally designed to be made out of metal or plastic and not out of plaster.
How to get high quality detailed casts without bubbles out of this detailed pieces;
Preparation of the mold:
Before casting I make sure the mold is clean. I wash it in warm water and mixed a bit of soap in it. (the one we do the dishes with) When the mold is
clean I shake the excessive water out of the mold.
I now lay the mold aside and start preparing the plaster.
Preparing the plaster:
Preparing the plaster for detailed casts means that the plaster is much more fluid as it normally is. A normal preparation for a cast means that I keep on
adding plaster until the plaster will keep lying on top of the water. In this case I will stop before this stage so the plaster is muck more like milk then like yoghurt. (hope this gives you some idea of the difference between the two consistencies I use for mixing plaster)
Before I go to the actual filling of the mold it is important to know that plaster will start to descent in the cup in which you mix it. Since the filling
up of the mold will take a while it is best to stir it every now and then.
Filling the mold:
Essential for making a good detailed cast without bubble is having a pipette. I use a cheap plastic pipette that is used within laboratory work. These
pipettes are made for quick use and then they will be thrown away. When you take good care of the pipette it will last a long time.
You can either hold the mold in your hand or lay it in front of you on a table in such a way that you can get a close look at it while working the mold.
You fill the pipette with the wet plaster and start casting the first piece. Remember that the cavities inside the mold are still wet. You squeeze the
pipette above the cup of plaster to make sure the air is out and the plaster starts to come out. You now set the pipette in the cavity you want to fill.
You can dose the amount of plaster that comes out of the pipette and you will see that the wet plaster will run through the cavity nicely. I does really
flow from the pipette into the cavity because of the fact that the cavity itself is still a bit wet in combination with the fact that the soap (in which
you washed the mold) acts like a sort of guidance for the plaster to flow more easily around.
For deeper areas like noses, bones, teeth, edges etc. The following tip applies;
If you lay the mold down on a table you can actually press on the mold just beside the point where you start casting with a pipette. By pushing on the
mold with a finger and pressing the finger away from the area you want to cast, you actually open op the cavity. (you stretch it so it opens up more and
gives you a better access to that part of the piece you are casting. Clean the pipette right after use so the plaster will not set in the pipette.
A few final tips:
- Make sure you let the plaster do the work. It is best it flows by it self in the cavities. Do not start casting from another end. Once you started,
keep on working from that side and (if necessary) push the plaster gently towards the area that still needs plaster.
- When you cast several pieces using a pipette, make sure you work the area as far as needed. This means when you filled up all the details go on to the
next piece. To totally fill op the piece is of later concern.
- Use a tissue to speed up the drying process once you have finished your cast. By laying it over the casted area it will suck out the moist rapidly.
After a few minutes remove the tissue and scrape the excessive plaster off. By tapping on to the side of the mold you will get a nice flat surface at
the back of the pieces you just produced.
Tips on normal casting will follow soon!
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Preparing the plaster:
