Sometimes you break stuff.
Knowing how to fix it is handy!


I was an utter arse recently when I tried to save a few minutes work by just using plaster when casting out a head.

Normally, it wouldn’t be an issue as good plaster is strong, and I have almost never had a cast break through neglecting to reinforce it, especially as this was just a master to clean up and remould. It was never intended for punishment.

Well, I trimmed the shoulders off and got impatient, and after cutting part way through the shoulder, decided to whack the crap out of it with a mallet in the hope such percussive persuasion would cause said section to leap helpfully off the remaining cast without whine or worry.

This did not happen.

Instead, the hollow shoulders suddenly broke and the head tipped back, broken clean through across a fold in the neck where presumably the plaster was thinnest.

I fortunately caught the head before gravity played its full measure of trickery, but even so, it meant my beautiful lifecast was now in three pieces instead of the convenient single article. Utter fuck.

Still, what’s learned is profit. Here is what I did to repair it, and rather jolly it was too.

Step 1: Get Over It
Invent your swearwords, mourn the loss of the imagined perfection and soothe the strain with a cup of tea/beer/shot of single/malt/all of these. Point is, if you’re still fuming, you aren’t likely to improve the situation with uninformed haste. Doing the first thing you think of very quickly and whilst swearing isn’t likely to help you, so make your peace with it.

Step 2: Check The Fit
The pieces were quite complete and readily fitted back together. Check the joining faces are clear of debris or loose crap.

Step 3: Stick It Back Together
I used PVA glue (the cheap white water based glue used in sealing brickwork for plastering) to glue the shoulder pieces back together. I left this for an hour or so and then I used plaster bandage to reinforce the plaster from inside the shoulders.

You could use superglue, that would work fine too but I had the other head to work on so I wasn’t in a hurry. The trick with repairs like this is to accept the time penalty, and not to hasten things too much or else incur further error and damage.  I leave the glued parts alone for an hour and then carefully back it up with some plaster bandage to add some mechanical strength.

Plaster bandage is used to carefully supply support whilst the glue dries.

Popping the head upside down into an empty plastic paint kettle (a bucket filled with sand or gravel is an excellent device for holding peculiar objects at convenient angles – see this video & post on supporting a tongue mould I did a while back) I apply glue to the broken edge of the neck.

Apply a generous amount, and seat the shoulders in place, ensuring that it sits at an angle at which it can remain – don’t need the shoulders falling off when your back is turned.

With sufficient glue applied, you will no doubt get excess squidging out as the plaster faces meet. If so, wipe this clean with a damp cloth or tissue (I keep a pack of cheap wet wipes on hand by the bench) before it dries as this will be a pain to do so later.

Ensure to wipe clean any beads of excess glue which creeps out of the join before it hardens.

Step 4: Reinforce the Billy-O Out Of It
Whilst the head is still inverted,  some scrim fabric and a runny mix of plaster is used to reinforce the inside. The runnier plaster is so that it grabs a hold of the existing plaster better. Were I to add a thicker mix of plaster then it will have its reduced water content sucked out by the drier and absorbent making it a weaker join.

After an hour or so,  the whole thing is sound and secure. It doesn’t look especially pretty but now nothing will drift or loosen. I can now mount this to a board and make good.

Once the head is leveled and attached to the board with screws,  a batch of plaster is worked into the open shoulder ends and any cracks, bubbles or deficiencies which need filling or leveling out.

I like to scrape it back just as it sets to smooth it and rinse water as it hardens to achieve an alabaster smooth finish.  By using a weaker plaster to fill the remaining holes and cracks, I am less likely to inadvertently damage the cast head itself with the scraping and smoothing tools.

The finished repair, ready to master mould.

For a more extensive example of fixing plaster, check out these three previous blog posts covering the fixing of a new face and how to mount the shoulders to a baseboard for secure fixture:

Right, I’m off back to the workshop to finish these moulds!



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All Aboard The Freit Train part 2

In part 2 of our discussion, Rob Freitas talks about the value of knowing about the unknowns.

He sheds some light on the importance of knowing to look at what was before and honours great artists like Gil Liberto ( who does incredible work for the likes of at Joel Harlow (Star Trek, anyone?).

Listen here or download.We’re on iTunes, Stitcher, iHeartRadio, Soundcloud and Facebook.

When going to trade shows and being asked to speak, Rob likes to share what he has known but he is there to be fed knowledge as well as to feed others. He doesn’t want to be the subject – rather he cares about the craft and wants you to care too. Thinking about provenance and what went before is a humbling way of uncovering the history of your subject matter, and is utterly fascinating.

When you think about the makeups from the original Wizard Of Oz from 1939, the list of makeup crew reads like a who’s who of the makeup industry – Jack Dawn, Max Factor, Cecil Holland, Robert Schiffer, William Tuttle, Charles Schram

Two more names that pop up are the perhaps little know Josef Norin ( and his son Gustaf (‘Gus’) Norin ( who were Swiss artists who brought their talents over from a background in sculpting and moulding small moulds for jewellery. Gustaf was father of John and Robert Norin, both makeup artists with an impressive line-up of screen credits.

Another aspect we touch on is how many of us working can count on the lack of distractions we had from the internet.

Whilst it is fair to say that the internet brings untold knowledge to our fingertips, it also means we need to learn how to focus and channel what is important, rather than allow meaningless information to steal our time away.

Social media makes people aware of what others may think of them or their beliefs…this wasn’t something we grew up with in the pre-internet age. It is certainly shaping how people learn, and it’s important to identify what really matters so one can harness that information and power into a tangible benefit rather than an endless distraction.

Rob mentions a number of artists work, and links are provided below:

Thanks again for checking this out! If you enjoyed this podcast, please support us if you can by:

  1. Sharing the podcast on Social Media
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Till next time!

Stuart & Todd

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All Aboard The Freit Train part 1

Rob Freitas is one of the best-known mould makers in the industry and has a phenomenal reputation.

Not only is he incredibly skilled at making moulds but he has a passion for the provenance of the techniques which he uses and cares deeply to help interested parties understand so they can be better too.

He also will redirect much of the attention he gets to his predecessors and those peers whom he feels deserve more attention. It’s a very generous attitude which I believe is born out of an unabashed passion for the subject and a desire to fan those flames in others.  It comes from a very pure place and it’s not often you meet someone with that much knowledge, skill and wisdom and who also is phenomenally approachable and easy to talk to. He’ll no doubt blush to read these words.

We hooked up at a pub near the Millennium FX in Aylesbury where he was teaching a class that week, and a few of us slunk off to the lobby of Rob’s hotel to talk bronze age axe heads, seamlines and technology.

Rob, me, Ivan Bellew and Nat Reynolds. Good times!

The audio is clear, but there is some background noise owing to the nature of a public space. It was around 10pm when we started and we kept at it until around 0130…that’s how interesting it was. Just a magical few hours and I’m really pleased we could synch schedules to be able to sit down and talk.

Listen here, download or get us on iTunes, Google Play Music, Stitcher, iHeart Radio or wherever you get your podcasts!

In this first of two parts, we talk about

  • Learning lessons through failure.
  • The importance of looking at the past and knowing on whose shoulders we stand.
  • Shortened timescales and managing expectations of people who seek to learn and gain skill (it is my belief the relatively short duration of courses as compared with time-served apprenticeships)  can rob people of valuable lessons acquired through error and repetition).
  • Caring about the right things in order to be better.

Axe Heads and Allies

The reason I brought that axe head was to show Rob the seams in it – evidence of moulds which have been used to make essential life sustaining tools and weapons. Moulds have been aroud for so long, and it gave me a bit of  thrill to be able to have a modern day master mould maker touch a casting from an ancient mould and admire their handiwork 2500 years on.

(Incidentally, this estimation is based on a bit of research I did into bronze age artefacts. This particular head is a palstave, check out

The palstave head in question.

See – a seamline!

Ancient toolmarks presumably from attempts at sharpening.

This old artefact has seams, and we still face this issue in moulds today. A lot of what we do and the work involved is in overcoming the seams or minimising their impact or appearance.

In the effects world where cosmetic perfection matters, making a good mould with a great seam is important and has a dollar value later down the line! It is also one of those crafts which isn’t seen in the final images of the makeup on set, and as a result doesn’t always get the love it deserves. A great sculpt, application, design or paint job can be appreciated in person on set but the mould is nowhere to be seen.

It’s funny that even with the advent of 3D printing, stuff still often gets finished up and moulded traditionally to produce casts as it often is still the best way to make things. Mould making is such a key skill, and the abilities of those that do it well really deserve some attention.

As with learning and getting competent with practical skills, the path to success can be hampered by a desire or pressure to run when walking hasn’t been perfected.  I believe the way forward is to do something small, do it well and then scale up gradually.


We mention a couple of videos that are on YouTube which show skills at work – hand making globes from 1955 ( and a Disney video explaining the different types of rivet (

This was something Disney did to help the war effort, when training many civilians to make military equipment like aircraft required detailed explanations of manufacturing processes such as these. How better to explain these intricate and involved processes than with an animation, condensing time and showing materials in cross section.

Look out for part 2 coming very soon, and subscribe to use on iTunes, Stitcher, iHeart Radio and Google Play Music to name but a few!




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IMATS LA Makeup Demo #2

The second makeup demo was a triumph of old and new.

Latex and silicone working in perfect harmony, with a budget to make the tightest of workshop strategies proud! 

I used an existing lifecast mould I had taken previously – so admittedly that was a bonus but aside from that, this was s pretty low budget affair with high impact. This free workbook details everything for you – get it here.

Latex is often overlooked as people perceive it as this lethal material which has epidemic proportions of allergy.

Whilst it is true that latex allergies exist, it’s also true to say that most people don’t, and those that do usually know about it. That said, it is sensible to check and do a patch test to make certain if in doubt.

Overall time spent was about 6 hours sculpting, two hours moulding, 1 hour casting and two hours painting- that is spread out over a few days as there is drying/cleanup time involved too but the point is in terms of overall labour input, it was pretty economical.

Consider the first couple of hours I was pushing clay around trying to find the damn sculpt within the clay whilst pushing away demons of self-doubt and the realisation that maybe I can’t sculpt any more. I hope that’s reassuring to anybody else who has those psychological imps that know you so well as to point out your flaws and point at them with

Anyhow, the process from start to finish is covered in this free workbook to download.  Just click here to go straight to it No funny passwords or access required – just a solid PDF which I urge you to share and absorb if you or someone you know would find it useful.

Right, I’m off to the workshop. I have a couple of sculpts waiting for me and I can hear their whispering from here. Brand new tube of plastiline to break in too…..does it get any better?




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IMATS LA Makeup Demo #1


Trade shows like IMATS are a wonderful opportunity for artists to have some fun creating things that they might not otherwise get to do.

For some people, it’s to show off a skill or technique or new material. For others, it’s a chance to take chances, experiment and play with some ideas. To indulge in a little playing, pushing some envelopes or exploring with methods which a show schedule just wouldn’t allow.

This was my plan with this makeup. I wanted to do some makeups which were effective, relatively straightforward to replicate and understand, and that would be pretty inexpensive to make without requiring tons of expensive materials or materials.

This makeup was made using gelatine from Titanic FX in Belfast, on whose stand I was demonstrating at the show on Saturday. I have taught a few workshops over there in Belfast, and really enjoy it at their studio.  Check them out and the workshops and kit they have to offer at

As is my way, I like to drill deep into the techniques behind how something is done. If you have been following me on Instagram then you may have seen me putting up live progress reports when I made this a couple of weeks back.

If that had piqued your interest, or if you didn’t see it but wished now that you had, then this workbook may be of interest to you.

Just click on the image or here to download your free workbook. Literally free. No sign in or passwords – just detailed explanations of my process.

  • Have a read, and pass it onto a friend if you have a prosthetic buddy or colleague.
  • Let  me know what you think – I worked hard on it but there is sure to be some errors and ommissions, so if you see something or want to know more, then please let me know!
  • Comment below or drop me an email

Till next time –


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IMATS LA 2017 was a blast!

I landed last night and wanted to get this down whilst it was still fresh.  IMATS was a great time – I lost count of the amount things I saw which almost had my eyes popping out of my head.

Check out the new podcast episode!

I went to the first ever IMATS in 1997 at the Beverly Garland Hotel, mainly as I wanted to meet the mighty Dick Smith and hopefully see my other makeup heroes.  Here I am attending an LA IMATS on the 20th anniversary as a speaker. Pretty special for me.

This is a review of my IMATS, my perspective. I know there was much there that I didn’t get to see as it is a huge show in a huge venue. I was doing demos and talking to lots of people, so every attendee’s story is going to be different. That’s the beauty of these events – lots of people seeing the same thing but all seeing something different. Also this post is not a ‘making-of’ for the makeups….that’s the next one! I’m on it.

Todd and myself on stage at IMATS.

Of particular note was all the things Lost Boys related, and it was a real joy to get up close and examine the moulds and pieces at length. I’ve been a fan of that movie since I saw it as a teenager and knew every scene inside out.

To be able to linger and look was quite a privilege. Talking at length about it with Greg Cannom personally was also an hour of my life that I’ll never forget! 

There was a display in the makeup museum featuring original moulds, prosthetic pieces, dentures and lenses as well as the 30th anniversary (yes – The Lost Boys is 30 years old!) panel talk featuring cast members and makeup artists Greg Cannom, Ve Neil and Steve LaPorte.

An unexpected treat was that the panel kicked off with a live performance of the movies’ theme ‘Cry Little Sister‘ by Gerard McMahon.  Massive nerdgasm!



A foam appliance from the original mould. You can see the makeup has a large single forehead appliance wth two smaller separate cheek appliances.

The plaster mould which clearly shows the staining from multiple foam runs.

There was even several sets of contact lenses there to see. They were very effective and added a huge amount to the character. Lenses have always fascinated me, as they are not something I personally have anything to do with outside of the occasional daily disposable.

What I like about the opportunity to study at length something which seems familiar (but actually isn’t when you study it) is that you can abstract it and see the item as series of shapes and colours. You can identify it as an object made up of a series of choices and that then makes it something obtainable, something which you too can make if you cared to take the time to do so. That is true magic right there!

The vampire dentures were also a joy to study, as I tried from a VHS freeze-frame to copy these when I started out playing with makeup. Indeed- I owe a lot of my enthusiasm for makeup to this film and the effects in it. To be able to look at the real things and understand what I was seeing felt a little like the closing of a loop. Pretty special.

The panel was good fun. Moderated by Paul Davis who is writing a book about the movie (he also did one on An American Werewold in London and a documentary about Fright Night….I recommend all of these by the way!) we heard from the makeup team as well as a few cast members about their recollections of that time in Santa Carla, the murder capital of the world.

Also was the pro night on Friday which kicked off with the launch of Steve Johnsons first volume of RUBBERHEAD: Sex, Drugs and Special FX.  Michael Key interviewed Steve Johnson and Sandy Collora, and they chatted about the collaboration which brought this incredible work onto the bookshelf and its long journey.

As is usual at these shows, a great many live makeup demonstrations took place, and none are more involced than those done by Thomas Surprenant who has made quite a reputation for massive, full body makeup demonstrations.  Always a tour de force, it was a joy to watch the guy work hard and he even allowed me to lend a hand for a time.

A sweeping panorama of the stage and seating area taken from the ‘Battle of the Brushes’ stage – this was on Friday during setup. The calm before the storm!

As to my involvement, I had my talk on stage which I shared with Todd Debreceni where we discussed some of the important aspects to learning the craft. As usual, my angle is one of ground up, no fluff or sales pitch but an honest discussion about the nettles one must grasp if you are to make real progress and get better.

The content itself will be another blog post and a podcast, as we agreed the material was so dense that it needs its own post where we can drill deep and get right into it.

Podcast Merch T-Shirts! Check it out!

I spent Saturday with Titanic FX, where I did a demo of a worm infested makeup (more on that next time as I have documented the making of it from start to finish) and on Sunday I applied my ‘bug-eyed Hypno Todd’ to my podcasting buddy Todd Debreceni on the London Brush Company stand. More on this next time!

Please drop comments down below or write to us at Let’s hear your thoughts!

Till next time –


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16-rob-smith-master-of-blood-pt-2Rob Smith continues his chat with me about foam latex, blood and other FX related goodies.

Also, Todd and I talk about our favorite podcasts, and whether or not the word ‘mustard’ is actually an expression.

Some news: Todd and I will be at IMATS 2017, 13th-15th Jan 2017. How about that?
(Check it out at

You can also get the podcast on iTunes, SoundCloud, iHeartRadio, Stitcher, PlayerFM, MyTuner….I mean, we’re all over that interwebs. Subscribe to us on you podcatcher app, and get every new episode.

Email us at the usual address,

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Blood ! Podcast #15!


It’s something gets thrown around a lot in film, TV and theatre. There’s bad blood, good blood, mudbloods, blood thicker than water and blood brothers. 

This episode we’re talking about blood, and our guest this time is Rob Smith, blood master as well as an all-around effects bod. He also runs a lot of foam, and makes exquisite soft foam appliances which you really need to feel to appreciate.

He makes his own pieces but runs a lot of foam for other people, and you’ll certainly have seen his work if you’ve been to the cinema in the last few years!

Blood needs to be a number of things:

  • The right colour
  • The right opacity
  • The right viscosity

It also needs to be:

  • Safe to use (skin, mouth and costume)
  • Easy to clean up

As a product, there are lots of different kinds of things which can be classified as blood. For example, blood as a real biological product does things – like clot, dry, separate, form scabs and flake once dry.


One of these blood drops is real!

An artificial blood won’t do that, so to create all these different possibilities, there are blood effects products like the standard liquid, flowable blood that comes directly out from an opening in the skin to ‘clotted’ blood, scab, wound fillers and pastes.

Often these are made from the same sugar or corn syrup base, thinned with water or thickened and then coloured with food grade pigments to an appropriate shade. However, as convenient and mouth safe as that may be, it attracts flies especially when shooting in warm climates.  Sugarless bloods, drying bloods which are alcohol based and even specialist bloods for use in eyes and mouth are available for use where appropriate.

All this means, of course, a large amount of product range, which we touch on a bit with Rob, who makes a lot of blood, but focusses mainly on the flowable blood which gets used in rigs to pump and splash around on set.


Blood Gags

I’ve done a fair few blood gags (a lot of necks, weirdly), that is makeup effects which use blood that gets pumped on cue, and thinning blood so it flows right under pressure means a fair bit of effort and testing to ensure it looks right.

The thing about a blood gag is figuring out what kind of tubing to use and where to put it – we could do a whole podcast just on the ins and outs of blood gags – but there’s all that stuff under the piece which needs to be right, and then the appliance over the top is just to hide that plumbing job underneath.

If blood is too thin and translucent then it doesn’t look right, and if it is too thick then it won’t move and spray correctly.  The fact it needs to travel under pressure, through various different tubes and connectors etc.  All that changes the way the blood flows, so knowing this and doing lots of tests to make sure you have a good idea about how that particular gag is going to work is important.


Interview with Rob Smith

blood-label-copyAnyhow, listen to some bloody wisdom from Rob Smith, which we recorded in his home.

It’s worth pointing out the guitar you’re going to hear is Rob, plucking away just for fun as he showed me his guitar collection hanging from the walls in the lounge.

Pretty cool stuff.

We chatted for a long while so I’ve split this up into two hour-long chats, and we shall release part 2 within the week.


Rob makes a great blood for use on silicone appliances which flows and smears realistically and which doesn’t ‘bead’ up on oily surfaces which can happen with many water and syrup based blood. You can see which is which in this comparison!


Teaching & Learning Makeup FX

Being in Belfast this week teaching at Titanic Creative Management made me reflect on the various kinds of learning environments I see so I talk a bit about some of the issues I see in colleges, namely that the institutes often fail the tutors. They squeeze the goodwill and best efforts of many tutors and some don’t even appreciate the requirements of a course leaving tutors woefully unsupported.  I think many of the tutors do a good job despite their faculty rather than because of  it.

I have said before that makeup is often underestimated,  people may attend a makeup course because they themselves wear makeup so…how hard can it be,  right?

The majority of people I’ve met at colleges really do care about being there,  and some are outstanding. However, I’ve been to other places which felt like it was a crèche for big 20-year-old kids and you know that shit wouldn’t  truck if they were an apprentice.

I care about the craft side of things and I don’t want to see people wasting their time.  When college attendance is ruled by ‘do you have the money’ rather than ‘look, this is hard work…do you really want to do this?’

College makeup school tutors, I salute you.

There are people who just won’t turn up on time and who skip entire weeks, suddenly to return at the last minute as assessments rear their head. Then that poor tutor has to give up endless extra hours to mend that as best they can because the college took on someone that frankly doesn’t want to be there. If that was a freelance apprenticeship, I can just fire you for being shit.

If you’ve paid to be there, it shifts the power so the relationship between the learner and the teacher is transactional rather than one of mutual reliance. Read that original blog post here:

There is of course nothing wrong to pay to learn, I myself pay to learn things and am glad I can do so. However, the people taking the money at colleges and universities are not directly responsible for dealing with the learners on a day to day basis. Private makeup schools, however, usually have a closer relationship with their attendees, and as such, I have seen a marked difference in attitude – they are there for a short time and really want to be there. I suppose also college is the first logical step after school, so many are attending fresh from a school education and are younger. I know I did!

This is what goes through my head when I get asked three times a week which college is best etc. or whether they should go private. It seems a college will provide an academic qualification, and that is the appeal to do that over a private course.

However, If a large portion of the course is endless theory which is not required on a set, you can become ‘qualified’ whilst being utterly useless. If you pump out thousands of students like that, that serves nobody except the facility which charged you a small fortune for the privilege.


Will Digital Kill The Practical?

Lots of people ask this question, and the changes are new relatively speaking so a thorough understanding of the future effect of it is not something any one person has a full explanation for.  The truth is it isn’t going away, it isn’t taking over everything and it isn’t something that you can’t take part in.

Lots of people are getting in touch and asking for survey responses, so it’s clearly a hot topic. It even made it to the editorial of the latest Prosthetics Magazine (well worth it by the way, I’d recommend it. Get yours here in print and digital: )


Transferable skills needed in both digital and practical work remain good basic abilities: good design, ability to render and understand anatomy, and using reference to constantly upgrade what you know. The computer doesn’t do it all for you – there is a skilled person behind the keyboard. You could be one of them.

There are a lot of areas which come under the digital umbrella, and the trick is to find a way in if you are interested. If you like sculpting then check out the digital sculpting programs and photo retouching is usually done in Photoshop. This is a paid for programme but you can still get CS2, an old version for free here:

Also check out the free image editing software from GIMP:


Digital Sculpting

Digital sculpting is changing a lot of things slowly, and programmes like Zbrush and Mudbox make it possible to apply the same editing qualities of a Word document to a sculpture. Clay is great and I recommend using it – you don’t need to choose just digital or just clay, I think using both is important. However, for no money at all, you can introduce yourself to the digital sculpting

To check out and download Sculptris:

The stripped down version of ZBrush is called Zbrush Core, so check that out here:

Keep on trucking! Remember you can get in touch through email on, through our Facebook Page: or comment on the blog post,

  • Stuart & Todd
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Podcast #14 – Scanners & Schoonraads


This podcast takes a little look at the influence of digital technology on the practical effects workflow.

Download it from Soundcloud, iTunes or play right here:

Bear in mind the problems we try to overcome – namely to create an illusion which appears real such as a decapitation, an injury taking place or some kind of transformation – these issues are the reason that we strive for new and better methods. That desire to create is the wind in the sails, and we have always used the best available to get that.

Digital has affected everything, every industry and we have changed along with it. Despite that, it’s a tool and one that many of the practical FX side view either with suspicion or glee. We wanted to chat about that and start a conversation about what it means and how we can work with it rather than against it. After all, I think that’s the ultimate fear, and I think it doesn’t need to be that way at all!


My head scan. Painless, but tragically accurate.

I talk with Steve Johnson briefly about his upcoming volume Rubberhead, Todd reveals his pixelated past and John and Tristan Schoonraad of Lifecast at Elstree studios chat about their 3D scanning work!


Tristan Schoonraad creates art using 3D scans and plays with scale – miniature to massive with equal accuracy!

Email us or drop us a comment on our Facebook page! Look us up under Battles With Bits Of Rubber!

-Stuart & Todd

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post-adOne of the biggest tales among mould making folklore is the curse of undercuts visited upon unfortunate souls who failed to spot them.

I figured it would be a worthy subject to throw some spotlight on and look at what undercuts are, why they are a problem and what we can do about them.

What is an undercut?

Essentially, it is a shape which has surfaces not visible from a single angle. In itself, it isn’t necessarily a problem unless a rigid mould is being made of that undercut. Mould pieces are pulled away from their casts in a single direction, and if that undercut goes the opposite way to that direction, then you could be in trouble.

They can be slight or extreme, and most commonly in FX stuff it is down to the curvatures found in a shapes of the human body.

To demonstrate the principle, imagine for example making a plaster mould of a plaster sphere. In order to get the mould open and make the mould in as few pieces as possible, the mould would need to be in at least two halves, and those would have to be made to meet exactly in the centreline.


If one half was slightly larger than the other then one half of the mould would pop off whilst the other essentially was locked in, and either the mould or the sphere will need to break in order to separate them.


The alternative is make the mould in three or more pieces to make it much easier to open (more work and an extra seamline to fix) or to use a flexible material such as silicone which is able to flex and allow the pieces to separate more easily (extra expense and time). Either way, if there is an undercut then it needs addressing.


Common places for undercuts on a face can be on a nose, where the wings of nostrils flare out and then return to meet the cheeks and top lip. It’s possible a nose may have a more obtuse angle here and consequently present no undercut, but often this is not the case.

Even a slight undercut can cause rigid moulds to lock with something having to break in order to open the mould up, likely ruining the mould or pieces made from it. If the mould does finally open, then the broken areas will be seen in pieces cast from it.


Things than go ‘inwards’ on a positive such as a face cast will come ‘outwards’ on a mould of it, and these can be thin or fragile outcrops of material whose broken shapes will be visible in the appliances, usually meaning a do-over. Not a welcome prospect.

Anyone who has made a number of moulds will certainly have come across this phenomenon and hindsight is 20/20 so there are a number of strategies  exist to deal with them.

Solutions to the problem


Naturally, the easiest is to make moulds of everything in silicone which can be soft enough to bend where rigid materials would break. This may seem like a logical answer and it may indeed solve some problems, but let’s not be so prescriptive about that.


Ears are notoriously undercut with their many curves and indented negative shapes. Filling these in and remoulding them as simplified shapes helped make these ears pieces work well, especially with a silicone negative.

For one thing, silicone is expensive and often needs a supporting jacket to keep it in shape so it adds time, expense and possibly size to a mould – which if totally necessary is worthwhile. However, if something can be made quicker, cheaper, lighter and smaller without silicone then it isn’t a terrible idea to do so.

Possibly a silicone mould won’t work, as the piece in question may need to a rigid mould such as when casting latex pieces – plaster is used to cast latex because it is porous and absorbs the water in the latex – silicone moulds are waterproof and make casting latex pieces much trickier.

Also, it isn’t just about being able to open the moulds, it’s also about getting a mould to close without touching. The majority of silicone appliances need mould surfaces to be prepared with an encapsulant of some kind.

If parts of the mould smudge past each other on closing, you could damage that delicate surface and not know until you’ve gone through the process of running that appliance. Not until that material has cured and the mould opened will you know whether or not that mould is doomed to fail the same way every time.

Multi-piece moulds

Another is to make a mould in more than one piece to allow those pieces to be opened in different directions. This is often a tactic used, sometimes if there isn’t a major undercut because it simply makes it much easier to open the mould. The trade-off is that a seamline is inevitably created, (although a good mould will yield a thin seam which is of no major consequence).

It may be that a tight fitting or large mould requires a lot of pulling and prising to open, and these stresses on moulds can cause unwanted damage (especially if many casts are required from the mould), making a thin seam a fair price to pay for a much easier opening experience.

This is where good mould-making is a great asset in a work pipeline where multiple casts need extensive seaming. A good mould yields pieces which are easier to repair and so have a real dollar value in the long run.

Change the sculpt

Another is to sculpt in such a way so as to cover undercuts with the soft sculpting material. If making appliances then the pieces will likely be made in a soft material like a silicone gel or foam latex. Assuming the undercuts which are covered with sufficient thickness of plastiline cover the undercuts then the resulting appliances will also be soft enough to flex around any undercuts and there’ll likely be no problem.

Sometimes a sculpt is modified in order to address undercuts, and if increasing a thickness here or extending an edge there or cutting something back doesn’t compromise the design too much then it’s a perfectly sensible way of fixing that issue.

Also, any cutting edge or overflow clay which is laid down can fix the same issues – the thickness of the clay laid down can cover minor undercuts just the same as a sculpt. The principle remains the same – the mould doesn’t get to meet the cores surface at a point where an undercut would be created.

Modify the core

Finally, and possibly my favourite, is to fix the core before sculpting begins. This may involve taking a tool to scrape away the plaster on overhanging eyelids extended to the weight of casting material used during the original lifecast.

It may involve filling in nostrils with clay, flaring out necks or extending sections in order to provide a flat and smooth area to put keys, bolt holes, touchdowns, pry points or whatever else may be necessary to make a mould work well yet would otherwise be tucked around the back of  a shape and would make opening tricky.


Clay added to the plaster original creates a flared out area. Mould this to cast out duplicates with a flat area built in to place keys, overflow and pry areas later.


This is often a great way of taking the problem away early on (although admittedly at more time and expense as a mould is then usually required of this modified version) as the mould is then made purposefully from the outset to function at its most efficient.

Being able to get a piece out of a mould easily is a great feeling when THAT part of the process is at the tail end of a job when time is at its least available.

I’d rather over-engineer a core and make a piece fall out of the mould than rush through things and be praying every time it came to open the mould.

Usually, the solution is a mixture of these techniques, depending on what you have most of – time, money or nerve.

Have you had any howler undercuts in moulds? Have a cautionary tale?  Let us know and we can feature them in a post! Email us at!

Happy Moulding!


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