You’ve got your original master plaster lifecast. Mould it, don’t drop it!
In the blog post from June, I took a look at prepping an original plaster life cast. This post takes a look at the moulding part. We want to mould this plaster original so we can make more in different materials.
It’s often the case that many processes necessary in makeup effects and prosthetics are not immediately obvious when faced with the final makeup. The appliances on the skin are born out of various stages, and each one needs to be done right.
The head now fixed onto a baseboard and trimmed with every surface smoothed and perfected is ready for moulding. The usual way is to make a silicone mould with a rigid jacket, as silicone is typically the best material as not much sticks to it, so it’s ideal for making plaster and resin copies. However, silicone is also an expensive material, so on occasion, the back half of the mould is made from whatever rigid jacket material is used.
The back of the head is typically smoothed plaster, and there are usually few significant details on the back of the head and shoulders, so the silicone that would otherwise be used here is actually not serving any great purpose.
A series of videos and blog posts I did a while back documenting the process of making a fibreglass and jacket master mould of a full head and shoulders. I am working on a new mould using a slightly different method at the moment, so I shall feature this soon. However for now, please check out the video playlist (there are three videos) which also features workbooks that contain step by step information.
In the UK, many master mould jackets are done using fibreglass and polyester resin. This makes a great lightweight rigid jacket which is very strong in thin sections, but it is also notorious for its persistent smell and messy working conditions. It can also be done using plaster (a strong stone such as Ultracal 30 in the US, Crystacal R or Herculite in the UK), a urethane such as Easyflo 120 mixed with Polyfibres or even an acrylic composite such as Jesmonite or AcrylicOne.
To get the best and nicest finish, usually the head is clad in a specified layer of clay (usually around 10 – 15mm thick) and all location keys are fitted on this original clay layer. Onto this is then layered the supporting jacket, usually in two or three sections to make demoulding easy. It may seem a bit of extra work to make the jacket in more than two pieces, but depending on the shape and undercuts involved on the head, it may well stress the mould much less by being able to more easily pop the jacket off. Remember, you make the mould
Remember, you make the mould just one time, yet you may be called upon to cast many dozens of duplicates from it, so if any severe undercuts are observed it makes sense to be able to take apart the supporting jacket more easily to allow the silicone to be peeled off.
Once this material has set completely over this clay, the rigid jacket is then opened and the water based clay layer is removed. This may mean a good deal of scraping and digging to get every last bit out, but keeping this clay will enable us to estimate the volume of silicone which will then be used to fill it.
Check out the videos to see the process from start to finish. The detailed process is there in the video, but the downloadable workbooks are a valuable printable resource you can use to help follow along.
I’m in Glasgow at the moment, admiring the stone buildings that dominate the streets. I’m having a great time teaching a few classes here but the evenings will be decompression time, writing and podcast work. Stay tuned!