I wanted to try to mold and cast a prop. For my first casting I decided to also try cold casting which uses metal powder to achieve a genuine metal finish. Building the dagger is relatively cheap, casting is where the project gets expensive.
I will walk you through the project step by step from building the dagger and then molding, casting, and cold casting the Dragon Priest dagger, while listing all the supplies and tools I used.
• Band Saw
• Hand Saw
• Various files
• Hobby Knife
• Sanding Block
• Belt Sander
• Router/Table w/ .125" round over bit
• Scale for silicone rubber
• Hot glue gun for mold walls
• .25" MDF
• .75" Project grade Plywood
• Nitrile Gloves - latex will inhibit MoldMax curing
• Super Glue
Molding and Casting Supplies:
• Smooth-On Smoothcast 325 - 1 gallon - $82.64
• Smooth-On Ease Release 200 Aerosol Spray - $13.20
• Smooth-On Bronze Powder - 1 pound - $25.71
• Smooth-On So Strong Black Tint - $13
• Smooth-On Mold Max 10 - 1 gallon - $96.54
• 32 oz pack of 10 mixing containers - $7.10
• EVA foam to build up part line using less clay
• Foam Core Boards for mold walls
• A band saw can remove fingers very quickly if you don't pay attention. Proceed with caution when using jig or scroll saw, don't cut near or on your favorite antique.
• When drilling, make sure you don't accidentally drill through anything you don't want to.
• Spray paint must be used outdoors in a well ventilated area. A respirator or mask is recommended. Allow time to dry fully.
• Wear old clothes for painting. Chances are paint will find a way to get on your clothes.
• Put down a drop cloth when working with silicone rubber or resin. You will spill at least a few drops, if not more.
• Never handle metal powder without a respirator.
Reference Photos - The first step was searching for reference photos. There are many photos showing the profile of the dagger, but no pictures depicting the edge.
Initial Sketch - As usual I took to Google Sketchup and began drawing the dagger. I scaled the handle to my hand and came up with an overall dimension from blade tip to pommel of 22". I cleaned up the dimension to round fractions. For the thicknesses, I guessed. My baseline was the handle. I took a few scrap pieces of wood and determined the handle to be .75" x .75" square. I assumed the back edge of the blade to be .25".
I printed out two 1 to 1 scaled images of the dagger for reference during the build.
Step 1: Create the Skyrim Dragon Priest Dagger
To mold an object, you need an object. This is how I built the Skyrim Dragon Priest dagger.
I cut out the handle first from .75" project grade plywood, leaving extra at each end. I wasn't sure how I would assemble the dagger at this point. To create the grip on the handle, I used the band saw to cut a small notch on both edges of the grain side of wood according to my reference image. I then took a hand saw and connected these notches across the face of the wood on the front and back side. I used the belt sander to round the handle and then re-cut the notches.
With continuous notches around the handle, I took a small file and created the look of the wrap. I filed the groove to deepen it, then rounded the resulting edge. It came out better than I expected.
The cross guard was cut from .75" project grade plywood. I used the belt sander to get the rough shape, and then resorted to a sanding block. Later in the assembly I added .25" MDF to widen the cross guard as the raised blade detail was wider than the cross guard.
I glued the MDF to each side and used body filler to blend it to the cross guard.
The intermediate between the cross guard and handle grip is three layers of .25" MDF. Edges were rounded with a .125" round over bit on the router table. I glued this to the cross guard. Pay attention to orientation and squareness, ensuring it is centered. I re-glued this piece twice because I didn't glue it straight!
The pommel is .25" MDF sandwiched between .75" project grade plywood. The pommel started out as a block with the belt sander helping to achieve the curved shape. Body filler was added to blend the pieces together.
The blade started as .25" MDF. I cut the shape on the band saw and left a tang for attachment to the handle. After cutting the shape I wondered if I should have used plastic since the sharp edge of the blade is so thin. I used a plunge bit on the router to thin the MDF and it was not too brittle. I calibrated the plunge bit so that I'd have a 1/16" blade thickness. I used a sanding block to form a point on the blade edge.
I spray glued my paper template to the blade and used that as a guide for the router cut.
I added polystyrene to the blade to achieve the raised curving details. To create the thin raised detail, I then cut a .25" MDF strip to .25" wide. I used my router table to round the edge on both sides with a .125" round over. I made a few shallow relief cuts with the band saw to aid in curving the MDF strip, to avoid breaking it. I broke one piece and super glued it back together. This raised detail angles down to the tip of the blade and angles out. To keep the width uniform I cut a think piece of polystyrene to act as a guide. It's the limit of the body filler and where to stop sanding.
I then super glued the polystyrene guide and MDF detail to the blade. I added the body filler, wiping away any excess the best I could.
As soon as I exceeded the pot life of the filler, I used the hobby knife to cut away excess body filler while it was still 'green'. The body filler will reach a point where it's still soft, but not too soft to sand. Shaping it now will be much easier than when it's fully cured.
I also used body filler to fill in a few gaps and a divot made by the router on the blade.
I used a flat file to create a slight ledge to the raised detail per the reference images.
Assembly and Paint
I cut off the extra knubs of the handle and glued everything together. Pay attention to ensure pieces are square and centered. I used rubber bands to maintain tension.
I drilled a hole in the cross guard down through the handle to accept the 'tang' of the blade. I modified the hole to fit the blade 'tang'. It turned out to be an ugly cut, but I epoxied it together and it works. What I should have done is drilled a hole in the blade and handle and used a small steel dowel and epoxy for a cleaner connection.
I sprayed the dagger in primer, hanging it on a bent metal coat hanger. I used more body filler to fill in a few areas that weren't smooth and flush, and to shape the blade tip as the detail wasn't very crisp. I should have used an air dry clay, it would have made the shaping of the tip a bit easier. Body filler is not the best for fine detail.
I painted the dagger again, sanded it down to prep for the final paint. I used hammered metal paint.
This paint works best on horizontal services, so I painted each side of the blade separately to achieve the maximum hammered effect. the heavier the paint, the better the texture. Next I create a mold to make duplicates.
Step 2: Supplies for Mold Making and Casting
Supplies for Mold Making and Casting
• Mixing Sticks
I had never made a silicone mold or cast plastic. Research pointed me to Smooth-On for product and as a resource. I determined what I thought I needed based on researching the site, and then called their technical help to confirm my idea was correct. Smooth-On support gave me some great advice and was very helpful. I initially had selected a medium curing resin, but Smooth-On pointed out that I would want a fast curing resin since I was adding filler. Extra cure time would provide the filler time to sink to the bottom. The three minute cure time of Smooth Cast 325 turned out to be plenty of time.
Molding and Casting supplies are where this project gets expensive. I really wanted two daggers, so casting was the answer. I also wanted to test out cold casting with metal powder.
Wood mixing sticks are not recommend as it could introduce moisture into the resin. I used wood paint stirrer sticks, but didn't experience a problem.
Before starting the process, my research involved searching through threads at the prop and costume making forum, www.therpf.com and reading tutorials at Smooth-On to learn the process of making a mold and then casting.
Step 3: Mold Making Part 1
This is my first attempt at molding and casting. I will tell you what I did, and what I would do differently. I made a fair number of mistakes.
Since the mold will be 2 part. Half of the mold is poured, then after curing, the second half is poured.
I found a board larger than the dagger. I hot glued the dagger to the board (which pulled paint off of the dagger later, glue isn't necessary), and shimmed the dagger with EVA foam so that the part line was parallel with the center of the dagger handle and blade. I used EVA foam to build up the part line and use less clay. Plasticine clay will form the part line for the Mold Max 10. The clay should create a horizontal surface centered around the entire dagger with no gaps. Heat the clay in the microwave (it has to be non-sulfur though). This will make it much easier to work. Get a few clay tools, this will make the process easier for nooks and crannies. A plastic spoon and knife will also suffice. For the most part, using my fingers worked fine. The clay doesn't have to be perfectly level, but try to get it as level as possible. You want a very good seal at the clay and object. Pay close attention to getting a 90 degree angle from object to clay to ensure clean seams in the cast.
I used foam core board and hot glue to create a wall. I formed the box to contour with the prop. I should have made a square box and not worried about extra silicone. A square box would have saved a LOT of trouble and time since I had to build the box for each half of the mold. The silicone I saved was minimal. The silicon should be 1" wider than the object. I was a little less than this on my mold. It makes adding registration keys and vents difficult.
The dimples are registration keys to ensure the mold fits together correctly. Without keys, the mold halves could shift, creating an uneven seam. I used the end of a paint brush to create them in the clay. I also used the paintbrush to create air channels. Create an air channel at any undercut to release any trapped air when casting. Clay was used to create a pour spout. Next time I will get a small funnel so that the spout is clean. I also want to look for thin wire for the air channels. Dragging a paintbrush in the clay, tends to drag it away from the object.
I used clay at the perimeter of the wall to ensure no leaks. Remember, you want the clay to form a 90* angle at the prop to ensure a clean seam when cast. The pour spout is at the pommel since it's the best spot for a pour spout. Channels for air bubbles should rise up to the pour spot. If you run them out the side, resin will leak out when casting.
I used Smooth-On's silicone calculator to give me a rough idea of how much product was needed. Mold Max has to be measured by weight. I purchased a digital scale because I plan to make more molds in the future. You could also use Mold Star as it doesn't require a scale, but due to the price I used Mold Max. It's much cheaper. My scale was wonky, but luckily I had another one. My estimates for rubber usage were correct despite the odd shape of the part/box. I used 2.25 pounds of Part A and .25 pounds of part B for the first half of the mold. The mix ration is 10:1. Also, make sure your mixing cup is big enough! Remember how much rubber you use for this step, you will use the same amount for the other half of the mold. Mold Max has a working time of 45 minutes, which is plenty of time. Don't forget mixing sticks either. It's best to lay out all your supplies before you start (I'll do that next time).
First spray the dagger and clay with mold release. When pouring the silicon, pour a small thin, slow stream from four to five feet above the mold in one corner, this helps remove bubbles due to the silicone stretching during the pour and prevents air bubbles from forming as the silicone envelopes the object. Tap the block the mold is on to help air bubbles dissipate. You will see the bubbles at the top pop as you do this. The first part of the mold from clay to silicone rubber took about four hours.
Step 4: Mold Making Part 2
This is a 2 part mold. I had to wait for the first half to cure before removing the box walls and clay and pouring the second half. Smooth-On recommends a 24 hour cure time. Once the silicone from the first pour is cured, flip over the mold and remove the clay. I left clay for the pour spout. For air bubble channels, I will cut those carefully after the second part is formed. I still need them to create the void. Use a damp cloth to clean up the prop and silicone. I was extremely happy to see that the first half came out perfectly.
I used 2 cups to mix the rubber I needed as the first time one cup was just barely big enough to mix. I used 1.125 pounds of part A and .125 pounds of part B in each cup. Use the mold release spray. USE MOLD RELEASE SPRAY. I forgot to spray the mold. UGH. Then (after using mold release spray) pour the second half of the mold, similar to the first - slow small stream from four feet up at one corner of the box. Once it's cured after 24 hours, remove the box walls and remove the dagger.
Since I forgot the mold release spray, I had to cut open the mold once it was cured. Registration keys and air vent channels were lost. Silicone only sticks to silicone. I only cut enough of the mold to get the dagger out. All was not lost, but my really awesome half mold, became a mediocre whole mold due to the error. I won't forget mold release again any time soon! I cut the air channels out the side, assuming I could just plug the leaks. That's much easier said than done. I ended up plugging the air channels with my fingers during the casting. Luckily resin cure time is only 3 minutes. The second part of the mold took about two hours.
Step 5: Casting
Before I cold cast, I made a test cast with just resin and tint.
Smooth cast 325 has a 3 minute pot life and a 10 minute de-mold time.Three minutes sounds very short, but it's plenty of time to pour.
Part A to part B mix is a 1:1 ratio. Tint is applied at 1 drop per 2 ounces of part A and B total when mixed.
I put the mold together and added water to get an exact measurement of how much resin I need. Remember the air channels I cut before. They leaked... A LOT. After finally plugging the holes enough, I had a measurement of 8 ounces of water to fill the mold. I mixed 12 ounces of resin to account for leaks. Write this number down. You will need it for every cast. Thoroughly dry out the mold before applying release agent. Any water left in the mold, will result in a frosted looking cast. I know this, because I didn't dry out the mold. While mold release isn't required, it will prolong the life of your mold.
I found two boards and clamped the mold together. Don't clamp too tight, you don't want to distort the mold. Clamp just enough to hold the mold together. Release spray was applied to the mold before assembly. Without registration keys, I had to pay close attention to how the mold lined up. Registration keys remove the guess work.
I poured 6 ounces of part A and 6 ounces of part B in separate cups. I added the tint to just part B (1 drop per 2 ounces of total resin - 6 drops), mixed the tint in B, then mixed A and B.
I poured the resin in the pour spout slowly, with the mold sitting upright, the pour spout at the top. While it does leak, the fast cure time means that mixing 12 ounces is sufficient. Once cured you should have a resin dagger. De-mold time is ten minutes.
My test cast was frosted looking due to water in the mold. The cross guard and part of the blade were not fully formed due to trapped air. I had only cut open half of the mold and undercuts on the uncut side were trapping air. It was also rubbery and very flexible. This is not a mistake, Smoothcast 325 is a clear resin and thus a gel. After a day the rubbery cast was completely solid.
I drilled in air vents with a 1/4" bit. I tried a smaller bit, but it didn't fix the issue on the second cast. Third cast came out looking right. So, what about cold casting?
Step 6: Cold Casting
To achieve a metal finish, I'm going to use metal powder. With fillers the de-mold time is extended to 60 minutes. NOTE: You need a respirator with metal powder. A dust mask is NOT sufficient. You don't want to breathe the powder in. You know that metal can cut you. Imagine tiny pieces of metal in the form of powder. Also be careful with clean up. I used tape to collect excess powder that didn't return to the container.
Smooth-On recommends mixing an equal amount of the powder in the resin per volume, but that gets very expensive, very quickly. I added just a small amount of powder to the resin. Since the filler thickens the resin, I mixed 8 total ounces.
For the cold cast, powder will be poured in the mold and then excess dumped out. Removing excess powder is crucial. I had a bit of powder trapped in part of the cross guard and blade tip, which meant the cast was slightly deformed. I powdered the mold, and added just a small bit of powder to the 4 ounces of part B before mixing part A and part B. The filler thickened the resin, which reduced leaks completely. I don't think powder in the resin made a difference as far as finish, but it was nice to stop leaks. I had a couple of swirls. I don't know if the resin removed the powder during the cast or the powder didn't adhere in a couple of spots.
My dagger came out looking very good despite the excess powder issues. Before buffing it will look brown.Buffing it with an abrasive pad will bring out the shine instantly. I then went over the dagger with Rustoleum black enamel paint and rubbed the paint off with a shop towel. This leaves the paint in the recesses and gouges, providing depth to the finish and contrast.Go back over with the abrasive pad to remove the black paint from edges.
If your mold is made well and air channels run to the top as they should, I wouldn't add any filler to the resin. Powdering the mold is sufficient to achieve a metal finish
Step 7: Conclusion and Lessons Learned
I made my first mold and cast (and a second, third, fourth, and fifth cast)! The process wasn't that bad. My prior experience had been with fiberglass, and this was much easier to work with. It's a ton of preparation work, but once you create the object and mold, casting is pretty easy (and quick).
If I was doing this again, I would consider using a brush on rubber like Rebound, and create a Plasti-paste mold jacket. This dagger, at 22" long is getting to the size where a mold could use either option. I wish I had made my box four sided. The savings in rubber with contouring to the dagger weren't worth the trouble. I had to build that crazy wall twice! I want to find thin wire or flexible smooth tubing for the air channels and an actual funnel for the pour spout. It makes for a cleaner mold.
I will also remember to use mold release when pouring the second half of the mold! Oh, and make sure your mixing cup is capable of holding everything you plan to put in it. Mix in separate cups if need be. And have mixing sticks ready!
I plan to do more molds, so I will invest in ratchet straps. Metal clamps are heavy and make handling the mold difficult.
Test casting is important. It was my third cast before I was happy with the result, and second cold cast (fifth overall) before that was acceptable. I've made 'a few' more daggers since then =). I don't know what I'll do with them all.
It's always fun to learn new tricks. I will now see if anything else I've made is ripe to be molded and cast. =) If you have any questions, let me know. Show me what you make!
Step 8: Video Recap
Runner Up in the
Halloween Props Contest 2015