Views 238 Likes Comments Comment
Like if this Guide is helpful



Plaster casting is fairly safe if you observe these safety rules when mixing.

*  Because plaster is very alkaline, exposure to high dust levels may irritate the skin, nose, eyes, throat and respiratory tract so     you should wear a disposable dust mask, eye protection and rubber gloves when mixing plaster.

*  Don't wear contact lenses when working with plaster.

*  Because plaster generates a lot of heat when setting - never use it to make casts of body parts.

*  Keep away from kids and pets.


1.  I find newspaper to be the best working surface as it's cheap and easy to clean up.

2.  Suss out your mould to make sure it's clean and dry inside because any dirt will come out in your casting .... ack !

3.  Because most flatback moulds wont sit flat on the table the best way to make your mould level is by using a ziplock bag with some rice or sand inside of it ..... these are easily stored after use for your next casting session or rice meal :)  You can use a box of rice or sand but then you have to be careful you don't get any in your plaster cast. 

4. To hold 3D moulds you need to get some stiff cardboard and cut into 10cm squares .... cut a hole in the middle the size of the mouth of the mould so that it can hang upside in a mug or something similar and then you just pour the plaster/soap/wax in ..... you have to make sure the hole is just right though otherwise if its too big the mould will fall through with the weight of the plaster/soap/wax and if its too small the base of the mould will 'scrunch'.

5.  The surface tension of the water in plaster has a tendency to trap air which causes pinhole bubbles or worse in your finished casting .... I have found that by swishing some talcum powder around inside the mould then tapping out the excess helps somewhat to prevent the air bubbles because it gets absorbed into the casting plaster and kinda sucks the plaster into the small corners where it sits.  There are other ways but this is the one that works for me.  Tapping your mould can also benefit but to do this you will need a square board with some kitchen sponges under each corner and then tap away with a hammer ..... lightly if you don't wanna wear your plaster.


1.  Most plaster mixes at a ratio of about 7:10 water/plaster however this can vary slightly and sometimes trial and error is the key here. 

2.  To mix the plaster without using scales - put some water in your mixing bowl and then slowly sprinkle the plaster in until it forms a mound above the water level say about 2cms ..... let it sit for a bit then mix with your stirring implement  (you can measure and calculate but this is a bit too technical for my liking and I always have another mould nearby that can take up the extra).

3.  Plaster should always be added to water ..... never the other way around.  You can use a blender to mix thoroughly for approx 1 minute but for small batches a spoon or stick will do the job.  It should end up being about the consistency of pan cake batter .... if it is too thin it will pour easily enough but you will end up with a very brittle end  result.

4.  After about 10 mins if there is any excess water on top of the mould then you need to just soak it up with a paper towel and then leave the mould to set for about 1/2 hour. 

5.  When it's time all you do is flex the sides of the mould gently and the casting should release easily ..... then it should be left to dry as per manufacturers directions.

 So there you have it ...... i've tried to keep it simple and hopefully this will help you all a bit and if anyone has any hints that may be helpful then please let me know and I will add them in wherever they fit :))

cheers and happy casting :))

Have something to share, create your own Guide... Write a Guide
Explore more Guides