Making a Blanket Mold: A free educational tutorial
An introduction to mold making materials and tools. In this tutorial you will become familiar with the basic mold making procedures and equipment.
Life's too short to waste it piddling around with a latex mold! Right?
Don't get me wrong I love latex as much as the next person. It makes a great mold. It's unbeatable in elasticity. It doesn't tear easily. It's an inexpensive mold making material. That's all great but what is your time worth? Can you afford to spend four to six weeks, maybe more, brushing latex rubber on a mold? No? Of course not. You have a life to live, things to do, people to see, money to make. Staying light on your feet , weaving and bobbing , keeping ahead of the crowd, those aren't just mindless catch phrases, they are the words you live by. They are the commandments of one driven to reach a higher plateau. Well my success oriented friend, this may be just the process your palpitating little entrepreneurial heart has been waiting for. With this system of mold making, a mold can be made in days not weeks or months. Not only that, but you can knock out duplicate molds so easily it almost seems criminal. Yes I thought that part would get the larcenous synapses in your gray matter firing. If anybody would, I knew you'd be the one up for a way to make money quickly and easily. No muss no fuss. Get in quick and get out! Move on to the next project. That style of thinking is right up your alley, right? Boy I hope I don't get caught in that alley!
Seein' as how you are one of those no nonsense "show me the money" kind of people and how time is money and money bein' the reason we're in business, we better git right to it or you'll start charging me directly.
That being said, and knowing the intelligent, well versed individual that you are, I know you are familiar with the nursery rhyme:
Bye, baby bunting
Daddy's gone a hunting,
To get a little rabbit skin
To wrap his baby bunting in.
Well forget about it my anxious little mold making friend. This blanket is nothing like that soft cozy rabbit skin blanket. This blanket is a flexible layer of cool rubber that will reproduce a plaster model in perfect detail. And that's way better than a fluffy litttle rabbit skin.
Here's the low down. What we're talking about is making a mold with a process that resembles placing a blanket over the object to be molded. Hence the name blanket mold. Essentially what you do is to form a 3/8" to 1/2" thick layer or blanket of urethane elastomer or silicone, (not latex rubber), over your model.
Daddy's gone a hunting and mother's gone a milking and you need to hunt for a base board for your project.
The first thing you need to do is hunt around for an appropriately sized board on which to mount the model or you could go buy one if you are so inclined. Because we are mounting the model on it we will call this piece of wood the mounting board ( how clever.) The mounting board should be 3 or 4 inches larger than the model all the way around. You can make one out of 3/4" plywood or if you're lucky you might find one ready made. I found this one on my wife's sewing machine cabinet. It's polished and lacquered up nicer than a barroom tabletop. It's mahogany, perfectly flat and, by coincidence, just exactly the right size. It's also free! A fella' can't pass up a deal like that. I'll just commandeer it for a spell. If you make your mounting board out of raw plywood be sure to give it several coats of acrylic sealer or lacquer. Then wax the board.
The other materials I have gathered for this project are:
Smooth-On urethane Elastomer, plastiline clay, acrylic sealer, spray release agent, paste wax, plastic tubs or buckets, spatulas for mixing and incidental items such as paper towels and disposable gloves. You will also need water based clay in an appropriate amount for your project. A link to Smooth-On and Compleat Sculptor can be found at our suppliers links page. The other supplies are available locally.
Adapt and Innovate
Mold making and model making are trades where the learning never ends. What I have done is to lay out the basic principles of making a blanket mold for you. A great deal, perhaps most of what you will learn about mold making, you will figure out on your own as you attempt this project. You are apt to make mistakes along the way. Do not let that deter you from your desire to grow and experience new avenues of creativity. You can do this. Adding to your store of knowledge is more important than doing a perfect job the first time out. Don't be too hard on yourself. With each attempt you will become more familiar with the materials and mold making processes. One day when you least expect it, it will all come together for you and you'll say "by jiggety that's it! I've got it. Dan was right. I can do this stuff."
As you have noticed the example that I have chosen to make a mold of is a plaster pineapple wall plaque; heretofore to be known as the model. The model has been previously painted and sealed with acrylic sealer so I do not have to do it again. If your model is made of a porous material such as unpainted plaster you will have to seal it with acrylic sealer. Krylon makes one such brand of sealer; another is Patricia Nimocks acrylic sealer. These products are available at art and craft stores. Take the time to do a good job preparing the model for the urethane mold. Seal it well with acrylic and spray it with a release agent. Polyurethane adheres amazingly well to improperly prepared models so do this part well.
What? You have looked everywhere and you do not have a pineapple wall plaque hanging around!
Since it is highly unlikely that you will have the exact same piece for your project, some of that figuring it out on your own stuff will have to come into play. Adapt the processes given to the best of your ability. You may come up with a better, quicker or cheaper way of doing it. Choose something simple your first time out like a wall plaque or stepping stone. Remember we are just trying to familiarize ourselves with the products and processes. (Actually I've done this once or twice, so its more you.) Once you learn how to do it in the manner described you can adapt the process to more intricate projects.
I have secured the model to the board with screws.
Below shows how I am drilling through the board into the model to give the screws a starting hole.
Also drill a few extra holes to act as vent holes. Gases build up in the mold material as they do in most of us and they have to be relieved. These gases will be released through vent holes. If you don't do this you could end up with giant pockets of gas in the rubber that could ruin your mold. This is especially true when making molds over porous models such as plaster models.
Plan 9 from Outer Space
The whole is more than the sum of it's parts. Rather than just following directions blindly you need to have a holistic view of the entire process in order to absorb it effectively. That's because once you see the direction we are headed, it makes more sense to your devious little reasoning mind. You can stop wasting brain energy wondering where is this going and focus your mighty powers of perception on the segment at hand. So now it's time to reveal the plan. We are going to cover the model with a blanket of clay. Then a hydrocal shell will be made over the clay blanket. The clay will be removed and a void will remain between the model and the hydrocal shell. This void we will fill with a urethane elastomer. We will then make another back up shell over the urethane mold. It sounds more complicated than it is. Trust me. On second thought maybe you better just follow your intuition.
Now that our model is mounted on the board, the next thing we need to do is put plastic wrap like Saran Wrap over the model. The plastic wrap will protect the model from the water clay which we will be applying over the model in the very next step.
Press the plastic wrap down snugly. It can extend out several inches from the edge of the model on the wood since we will be trimming back the excess later.
Press the plastic wrap down snugly. It can extend several inches from the edge of the model as we will trim it back later.
Continued on the next page.