Moldmaking Tutorial: 2 Piece Hydrocal Plaster Mold For Silicone Casting

making a two-piece hydrocal mold this is a follow-up video showing the construction of our bride of Biddy here in our store and many of you might have seen this at the recent Transworld 2017 and in this particular tutorial we'll be covering the mold making process of how we molded the head using a monster clay positive and molding that in hydrocal to reproduce in Platteville gel 10 so for those of you who were asking about the mold making process in the first video that we posted here is the mold making process and we'll be following this up with a couple more videos explaining the finishing techniques we use to both airbrushing and laying and punching hair so here goes this is our monster clay positive to begin with and this is just a clay positive that we pulled from a lifecast mold this is a gel 25 lifecast mold that we poured this into and if you want to check out that process you can check out some of our other tutorials or our lifecasting 102 DVD goes into that process in great depth but this is a clay positive that has a rigid foam core to support it and the first thing we need to do when we're creating a two-piece hydrocal mold is we're going to lay down our head since we're going to divide this up on two into halves on the plane there of the head once we've determined how that's going to divide up the front in the back we're going to lay it in a bed of scrap pieces of 2x4 and scrap wood and what that does is that's going to minimize how much water-based clay it's going to take to create that parting line as you'll see here in a minute now to create the parting line or that clay wall that we're going to build around our piece we'll be using our water-based clay our white modeling clay and this is different from wet clay this is just a low-cost modeling clay typically this is fired in the ceramic world but for our purposes this is a great clay for building mold walls and dams and things like that it's just a low-cost water-based clay that's easy to smooth out and it's cheap most importantly so when we have to build up clay walls like this in in a fast and inexpensive manner this is the clay we reach for now it's important to remember that this is a water-based clay and water-based clays do dry out and shrink and crack so when you do this step you want to move quickly and be ready to complete your mold within the next hour - if you make a clay wall like this it's a beautiful clay wall and then you don't make your mold immediately following this it's going to dry up crack and totally destroy the work that you've done so be sure that you don't build your clay wall unless you're ready to make your mold now I'm not really moving this fast I'm not tweaking on meth or anything I just sped this up just so you can get an idea of the overview of the process here what I'm doing is following the high points of the outside of the head along the ears and along the neck and the top of the head and what I'm doing here this is a very basic very simple way to make a two-piece hydrocal mold basically creating that clay bed and then I'm going to use a trowel or a putty knife to scrape that back down flat and what I want to do is get that to clay wall at about a ninety degree angle to the rest of the head or as close to it as possible and the reason you want a ninety degree angle is you don't want that one half of the mold or the other to be at a steep angle or a shallow angle that causes that to have a really thin leading edge that cracks off so you want that to be as much of as close to a 90 degree angle as possible and then we want to also go in there and clean up that edge and make that as precise as possible I like that clay wall to extend out from the piece at least two to three inches to give it a nice solid flange now one of the steps we'll need to do before we put our keys in place is we're going to cut the side and the top to define where our mold is going to be and this is an important step especially when you're starting out sometimes it seems extraneous but what we're going to do is just cut off the excess clay on the sides and the top of the mold and we're going to do that so that later on it'll be easy to strap this mold closed we won't have a difficult edge to strap or clamp the mold shut and the we'll be flat so that when the mold is turned upside down forecasting that it sits level on the top of the head so that's an important step that you'll see later on how we use that to our advantage as we're applying the plaster now we need to cut our key shape and for this we're just going to use a very simple key shape of just a tongue-and-groove key and we're going to create that just using a loop tool and the tongue-and-groove key this is probably the easiest kind of key to create but also a very effective key way and what it's going to do is accomplish two things it's going to key the front in the back of the mold together but also that tongue-and-groove shape keeps the mold from leaking when you're casting things like latex or poured materials that acts as a leak stop against any runny casting material flowing out of the mold and now we're need to do a final little bit of housekeeping around the edge of the clay wall and again as I mentioned earlier super important here as soon as your clay wall is ready you need to start on your mold if this sits for too long without a plaster mold on it it will start to dry out and crack so be ready to move quickly on to the next step of the mold and now we're just doing some last-minute clean-up on the flange we want that to be as clean as possible and we're ready to proceed with our hydrocal mixing now you might have seen this in other videos but we're going to cover this again just in case the way you mix hydrocal for this particular process we're going to start with about a half a gallon of clean water now obviously that amount of water will change based on the size of mold you're making for this particular mold about a half a gallon was about right to make one side of the mold now there are a lot of little details that make for good hydrocal mixing and one of the key things you want to remember is as soon as you measure out your water you're ready to sift in your hydrocal and you always want to use a tall enough bucket that there's plenty of room for that hydrocal you don't want to start with a bucket that's almost full and then start sifting hydrocal in it or very soon you'll be overflowing out of that bucket but basically what we're going to do is sift in by hand that hydrocal without disturbing the water just sift it in let it fall in naturally until the top achieves what's called a dry lakebed appearance and what that's going to do is that's the saturation point where our water is absorbed as much hydrocal as it can and that's key to getting a good strong end product with hydrocal it's very tempting when you're starting out to put a little bit of hydrocal in stir it up add some more stirred some more add additional stir it some more and the problem with that is you wind up with actually several distinctly different batches setting up within itself and you'll have cracks and little fissures forming later on and you want have near as strong of an end product so be sure that you use this method of sifting in your hydrocal and then let it sit for a good 5 to 10 minutes undisturbed and it'll absorb in and when when you do that you'll actually wind up with more working time and it'll be much easier to stir and most of those lumps will dissolve on their own now you'll notice I'm mixing this up by hand with hydrocal you'll find that you get much more working time if you mix it up gently by hand and just do the minimal and I'm not mixing just to make sure there's no lumps or any clumps of dry hydrocal down on the bottom if you use a drill a power drill to mix this up it's going to greatly diminish your working time so remember that when you're mixing this up so you get the maximum working time because you'll need it when you're making a mold like this now ready to put on our first layer our print coat on and the way this works with a hydrocal mold to get the maximum strength we're going to apply this all in one go we're not going to build this up in multiple layers of one layer of hydrocal let it set another layer let it set this is all in one layer and using the different stages of the hydrocal to make this work hydrocal goes through a stage initially where it's a very runny consistency and in that pourable stage or that pourable consistency it it's perfect for brushing on to the surface of a piece and capturing all that detail in the clay but it will very quickly transition you only have that nice runny stage for about a minute or two and then it transitions into more of a pasty kind of consistency like a slightly runny sour cream and at that stage that's where we're going to apply that over our print code and start building up the thickness of our mold and this particular layers we're building it up here our mold thickness is going to be right around 1/2 an inch and we want that to be a pretty uniform thickness and the reason for that is the next step once we get this applied all over get that kind of sour cream consistency applied all over our piece and onto the flange we're going to apply our reinforcement and once you master the different stages of plaster like this that runny stage and that kind of sour cream stage and then that final stage where it approaches like a mud like consistency once you master those different stages you can really exploit that to really make a nice mold in a very short amount of time and one of the things we'll need to make sure our reinforcement doesn't push through that layer is we don't want to apply that reinforcement until it starts transitioning into that more of a mud kind of stage and here we've applied that all over and our piece is starting to hit that kind of gelatinous mud like stage and we're ready to start very carefully applying our reinforcement and for reinforcement here we're going to be using some burlap some loose weave burlap we got at a garden supply and that can be cut into little squares as we've done here and I pre soaked that in some water you don't want to use that completely dry or sometimes it can cause your mold to warp now you can also use a fiberglass mat or hemp fiber as a reinforcement but again with this particular tutorial we wanted to keep this to a very accessible approach that with using materials most of you have fairly easy access to and now that our piece has transitioned more into that mud consistency you see that it's it's not slumping at all now it's very easy for us now to go around and check the thickness by running our hand around the outside of the mold and that's one of the reasons you want to have that nice clean edge because you see how easy it is there to just scrape along that outside edge down to the clay and you can immediately see the cross-section of the mold as you're building it up so now we're now that we've built up that thickness of hydrocal over the entire piece and you see that's great simplifying that form now ready to apply our reinforcement fiber and again we're just taking that damp that damp loose weave burlap and dipping that in some hydrocal and then carefully placing that over that hydrocal layer and real import it here and this takes some practice don't push that down and risk pushing it down to the surface of your clay we just need that for a reinforcement we're not trying to push that into the the surface too much so this does take some practice if you're new to this process make sure you try this out on a small piece and practice this method of building up a hydrocal mold and not on a piece that you've spent weeks sculpting on until you feel confident using this approach now you'll find that it really helps if in the reinforcement stage if the previous layer of hydrocal has been built up to a point that it's really simplified that form so you have a nice abstract shape because if you have if you still have a lot of curves and a lot of weird places and compound curves to cover it's harder to get that reinforcement fiber to lay down without accidentally pushing it through so be very careful as you're applying that and then also remember that each one of those little squares of reinforcement is overlapping the previous square and that ensures that we have one continuous layer of reinforcement all across the entire surface of our mold and also make sure that you don't skimp on reinforcement fiber around the flange because remember later on when you go to open this mold up that that's the part of the mold that's going to take the most abuse as that edge where you're going to need to pry it open or where it's going to be sitting or where it'll be strapped that's where the pressure will typically be applied to the mold and now once we've applied our reinforcement fiber ready to build up the remaining thickness of our mold overall we're going to have a mold that's about an inch and a half to two inches thick and we're just using the remaining hydrocal here in that kind of mud consistency stage and remember that when it the hydrocal hits this stage where it's achieved that mud like consistency it's very close to setting up so make sure you work quickly and deliberately and get good coverage all over your piece and don't stop because if you linger too long at this point you'll have a mold that will be really rough and very difficult to smooth out later on so you want to do as much smoothing to the mold when it's in this stage and not once the plaster is completely cured you'll find when plaster is cured it requires a lot of messy sanding and polishing and that just adds a lot of work that's totally unnecessary now for those of you who've watched our previous videos you know what that bucket is for to the left of the screen there on the left side that is my hand cleaning bucket and that is an essential part of this process anytime you need to clean up your hands make sure you have a bucket of clean water for cleaning up your hands and that you don't clean up your hands in your sink plaster water will totally destroy your plumbing so remember that and you can thank me later that's one of those little steps that will make everyone in your household happier and when you're done with that water you can put that outside that's all biodegradable it just can't go down the drain or it will turn your pipes solid now what we're doing here is again just smoothing everything out using a little bit of water on your fingers as a lubricant you can really smooth that out very nicely and we're just going to keep working that right up until the plaster sets and as an aside here sometimes we use the terms plaster and hydrocal interchangeably but hydrocal is a very strong tooling plaster not to be confused with hardware-store plaster if you do this method with hardware-store plaster of Paris you will have a very weak mold that will not perform like what you're seeing in this video so remember that that it's worth spending a little bit extra money either on shipping or on good quality hydrocal to do this process right we get a lot of phone calls where people are trying to do this with wall plaster and are always shocked to find out that it does not perform the same way and again you'll see that now we can smooth out those edges and just by using that clay wall as kind of our little ruler there as a guide to keep those sides straight we can get the sides of the mold in the top really nice and clean and straight and by working it until it sets up like this we can minimize any need to sand the plaster later on now eventually what you'll have is the plaster will transition to kind of a matte effect as it starts to set it'll lose that gloss and start turning kind of a matte finish on the top and start feeling a little drier and when it hits that stage you're ready to start polishing it with a piece of hemp and sometimes at that stage I just leave it alone for a few minutes and so I don't accidentally start leaving lines in it by polishing it with the hemp too early but as soon as it hits that stage where it's starting to matte over on the outside and get a little bit harder ready to use a ball of hemp to polish the surface now this is an optional step but again it's one of those little housekeeping steps in your mold making process that just makes for a much nicer mold and a much easier mold to handle it will get rid of any kind of sharp edges that could cut your hands or make it difficult to strap and close the mold later on now hydrocal when it sets it goes through an exothermic casting resin it'll get fairly hot to the touch and you'll actually see some steam coming off of it and then it'll start to cool back down and you'll actually see it go through a hot and then a cold spike and when it levels out at room temperature that's usually when it has a good handling strength to flip it over and start with the next side of the mold so this is a stage where we want to be really careful to not disturb our clay piece underneath or shift anything inside the mold we want to just very carefully turn that over and we're going to maintain a little a few of those boards on the opposite side to cradle that first half of the hydrocal mold and then we're going to very carefully peel away that water-based clay wall and here you'll see if everything has been mixed and applied properly that clay wall should very easily peel away from that cured hydrocal and another thing here is this is one of the reasons you want to make sure it goes through that hot and cold stage is if you do this too early you'll pull off chunks of your keys if you do this if you rush this stage so make sure you allow that the hydrocal to go through that hot stage cooldown and then level out at room temperature and then you'll be ready to clean off that clay wall and begin making the second half of your mold now we're going to do a kind of an abbreviated coverage of the second half because it's an exact copy of the first half with the exception of we will be releasing that exposed first half of our hydrocal mold now it's real important here to take the time to remove any clay residue any little clay scraps that might be stuck on your hydrocal wall just remember that the better job you do of cleaning up that edge the cleaner the mold is going to close you're going to get a much tighter seam because any clay that's left there that's not removed at this step will be a little bump in your final silicone casting so make sure you take the time to clean up that edge and you can also use some water just some clean water in a paper towel or a sponge to clean up that edge and wipe away any of that clay that will dissolve that clay and once that's cleaned up now you're ready to move on to releasing that hydrocal wall and for release we'll be using our molding wax and this is a pretty standard paste wax that you can use for this process the main thing you want to remember with this is do not use Vaseline now the reason we're using paste wax and not Vaseline is critical here paste wax will actually dry and then when we make our second half of the mold with our hydrocal the hydrocal will actually stay put on that paste wax Vaseline on the other hand does not dry and stays as this oily film and what happens is that naturally repels the hydrocal and not in a good way and causes that hydrocal to not build up and wants to just run off of that flange so real important here to use paste wax and release that entire seam area and also we applied that a little bit on the sides and the top of the mold for any kind of overflow of plaster and now we're going to speed it up so I look like a crack addled SpiderMonkey this is the second half so we're just going to do a quick overview of how this works again with that initial layer we brush it on when it's fairly runny then when it approaches that sour cream stage we build up our thickness and then when it approaches that mud stage we start building up the reinforcement and the final layer of our mold and again we want to emphasize that the overall thickness on a mold like this only needs to be about an inch and a half to two inches thick if you build up your mold thicker than that it's not necessarily going to make it any stronger it's just going to make it heavier and more difficult to handle later on so make sure you keep your molds efficient and just the right thickness to make them good strength and not an excessive burden on your back later on when it comes time to cast into that mold and there we have our second half and again we just polished that up with some hemp and we have a nice clean hydrocal mold and again we're ready for that to go through it's hot stage and then cold stage and again the way that works is it goes through a temperature spike where it gets really hot you'll actually see steam coming off the mold at that stage and then it'll drop down and actually get cool to the touch and then level out at room temperature and as soon as it hits that point where it's leveling out at room temperature that's when you're at handling strength stage where you can pry open your mold and I like to let this sit for a good hour and a half sometimes a couple of hours before I start D molding and the reason for that is if I D mold it too quickly the clay is actually going to be really soft and almost like a gooey mud inside the mold so if we mold this to quick what will happen is the monster clay just be a gooey mess inside so I like to let this cool down a little bit so that the clay is not soft and sticky and it's much easier to clean out of the mold and you'll see here that the clay split apart revealing our foam core inside and everything else released just fine so now it comes time to clean the mold out and get it ready for casting now again real important to remember that that hot stage when the plaster exotherm xand gets really hot that that will melt the clay and if you D mold it too quickly that clay will be very messy and very difficult to clean out of the mold so let it cool down a little bit it'll be much easier to peel that away from the inside of the mold and be sure to take your time peeling this away don't rush this process and don't use any kind of sharp pointed tools that could scratch the inside of your mold I like to use wooden sculpting tools or blunt steel tools to carefully remove any of those bigger pieces of clay and once you've removed all of the clay that you can by hand any kind of clay residue that's left over can be washed out of the mold using naphtha and naphtha you can find pretty much any hardware store is going to have naphtha most most Lowe's or Home Depot stores are going to have that and you can apply that just with a brush and what that will do is actually dissolve the clay so I don't recommend this until you've pulled out all the big chunks of clay because if you do this too early you're going to wind up with a big mess of of clay that's just turned to mush but if you wait on doing this just on there clay residue you'll find that this is a great way to remove any little bits of clay that are lingering and difficult to get to areas and once we've once we broken down any clay residue you want to use some clean paper towels to wipe that out and clean the inside surface of your mold and as an aside you'll notice the last half of the mold that was is still a little bit warmer than the front half that was the more difficult side of the mold to clean so that's a great example of making sure you give it plenty of time to cool down and it'll be much easier to clean out and now that we've wiped out all of our clay residue our mold is ready for casting now we kind of did this Quentin Tarantino style so go check our previous video for the the casting section where we show how to cast a Platteville jelton head into this mold and then stay tuned for the follow up videos where we show the finishing techniques used on this project and of course you can find all the products used in this video we'll put all the product links in the video description but the white modelling clay and the hydrocal and the mold wax and all the other stuff we used in this are available on our web store at brick in the yard com and if you want to see progress pictures from other tutorials we're working on or just be a fly on the wall in the video mold supply shop and studio and see some of the crazy things that happen here be sure to check us out on Instagram at instagram.com slash bitty multiply

Channel: Brick In The Yard Mold Supply

Views: 3,224,293

Keywords: plaster mold, hydrocal mold, plaster moldmaking, stone mold, resin mold, plaster casting, silicone casting, platsil gel-10, gel-10 silicone, prop making, halloween props, body parts, prop bodies, polytek silicone, bjb enterprises, monster clay, bity mold supply, brickintheyard, bride of bity, bride of frankenstein, silicone bust, fake head mold, prop head, fake body, movie prop

Id: c6WBotvMNvo

Length: 25min 2sec (1502 seconds)

Published: Thu May 04 2017