Casting With Metal Powders

Restoring antique hardware, casting statuary or bas-relief, learn how to easily simulate hot foundry metal pours using metal powders of all types combined with resin. Once cured the surface will age and patina just like all natural metals.

Now there is no excuse for not restoring or updating that memorable piece of furniture stored away in the attic or that old house project because it is missing a piece. There is no need to search antique stores or salvage yards for the missing hardware or applique, either. You don’t even need to find a foundry to reproduce that unique metal pull. Because you can easily duplicate any missing piece in metal, wood or marble, providing you have a piece to copy, with materials from the company whose motto is,” Reproduce Anything.” The technique used is cold casting and it is surprisingly simple.

EnvironMolds has been producing environmentally friendly molding and casting materials since 1998. They claim they have a product for any application. We put them to the test by creating decorative replacement hardware in a variety of metals as well as in wood in this project. It was as easy as they claimed it was, too.

To begin with we assembled the materials that we needed along with parts we wanted to copy. These included an engraved antique brass knob from a set of doors that had one missing as well as a glass doorknob and a wooden bureau pull from an 1870 maple veneer bureau. The materials included AquaClear resin, a water clear polyurethane resin, KastEZ an opaque ivory colored resin, and MoldRite25 a two-part silicone rubber, all three products by EnvironMolds.

We used EnvironMolds’ bronze, brass, mahogany, oak and marble casting media. In addition, we required a gram scale to weigh out the silicone. We also needed a few 16-ounce and 32-ounce cups, some mixing sticks, and a glue gun.

No Air Bubbles

One of the difficulties of mold makers is the fact that air introduced into liquids while mixing can and will interfere with mold making and casting. Professional mold makers use pressure pots and vacuum chambers to eliminate air bubbles. We learned a studio trick from EnvironMolds that accomplishes almost the same result.

We attached a power sander tool to the leg of a table using some electrical wire. (See opposite page) When turned on, the sander vibrates the table and in turn the mold or casting material. Any vibrating tool will do.

The vibrations drive out the air bubbles as they rise to the top of the mold. Don’t forget this important step or you will have imperfect results. If you don’t have a vibrating power tool, turn on the washing machine and place your molding and casting containers on top. Wash and mold-make at the same time.

LIST OF MATERIALS

MOLD MAKING

• MoldRite25—1-Pint Kit
• Hot Glue Gun
• Razor or X-Acto Knife
• Mixing Containers
• Mixing Sticks
• Gram Scale
• Vibrator ( Sander)
• Oven

CASTING

• AquaClear Resin 1-Pint
• Brass Powder 325 Mesh—1 lb.
• Mixing Containers
• Mixing Sticks
• 0000 Steel Wool
• Vibrator (Sander)

Making the Mold

We used a glue gun to attach the original knob to the bottom of a container. There should be at least an inch distance between the outside of the container and the closet part of the knob.

Now we are ready to mix the silicone rubber to create the rubber mold. MoldRite 25 is mixed at a ratio of 10 parts of A to 1 part of B. For this we use a gram scale. If the silicone is not accurately measured the material will not set.

We estimated the amount of part A needed to cover the knob to a depth of 1/2-inch higher than the highest part of the knob. This came out to be about 10 grams of part A. We then put a clean cup on the scale and poured out 1/10 of the amount we poured out for part A. In this case it was 1 gram of part B. We can’t forget to account for the weight of our containers when we measure either.

Setting the Tare Weight

To account for the weight of the containers we placed the empty container on the scale and pressed the tare weight button. This adjusts for the weight of the container and the scale now reads zero. If there is no tare weight button, we would have to weigh the container and then subtract it from the total weight.

Mixing and Pouring the Mold

When the MoldRite 25 was mixed to an even color without marbling we were ready to pour it into the mold. To further eliminate the possibility of air bubbles EnvironMolds’ advised us to pour at an exaggerated height in a very narrow stream by squeezing the cup to make a narrow spout.

We also poured in one spot allowing the MoldRite 25 to envelope the knob. This pushes out air. We poured enough to cover the knob 1/2-inch deeper than its height.

The good thing is that if we were short material, not to worry.  We could simply mix more MoldRite 25 without having done any harm to our mold making.

Once we finished pouring, we placed the container on our vibrating table and allow it to be vibrated for about 30-minutes or so.

MoldRite 25 takes about 3 hours to solidify before it is ready to be demolded.

Demolding

When the rubber has been set the finished mold was removed it from the container. We had to cut open the container to do so. Then to extract the knob from the rubber we turned the mold over so that the location where we hot glued the knob to the bottom of the container was facing us. Then we took a sharp razor knife and carefully sliced down opposite sides of the mold (about 2/3rds of the way.) See Step 8. Once both sides had been cut, we spread the mold open like a clam shell and removed the knob.

We inspected the mold for any lose particles and then closed using a rubber band to keep it tightly shut. We have now created our first finished mold.

Seasoning the Mold

We had to season the mold by baking it for 3-hours at 200-degrees F. This evaporates any residual alcohol. This alcohol, if left in the mold could interfere with the surface of the casting material. In addition, a cast sets better in a warm mold. So, it serves two purposes.

Making the Casting

To create the brass casting, we poured out equal parts of part A and part B of AquaClear water clear resin. It is just a simple matter of comparing the levels of each in two cups and making certain they are both the same. In a third cup, we spooned out an equal amount of the 325 Mesh (that is a very fine grind) brass powder. So, we had three cups all filled to the same level.

Since AquaClear dries rapidly especially in a warm mold (5-minutes) we will mix half the brass powder in part A and the other half in part B. Both cups were mixed thoroughly as the powder was heavy and tended to sink to the bottom. Once we had mixed both cups well, we combined one into the other, it doesn’t matter which. Then we mixed thoroughly again for about 45 seconds.

To start our pour we removed the mold from the oven (careful it was hot) and carefully poured in the brass mixture until it was filled to the top.

The casting was placed on the vibrating table to be vibrated as we did when we first made our mold. Since this set quickly we found that it only took 3-4 minutes of vibration.

Once it was set to the touch, we waited another 30-more minutes before attempting to demold.

Demolding

Demolding was straight forward. We removed the rubber band and spread the mold apart to pop out our finished casting. It was almost perfect despite a bit of flashing That was an easy clean up using an X-Acto knife. We also cleaned up any evidence of seam lines this way.

Finishing

With a little elbow grease and some four-0 steel wool we polished the knob to remove the resin on its surface and expose the brass. We could also use a buffing wheel for an even shinier surface.

The finished piece was an extraordinary copy the original knob. It is hard to distinguish from the original piece. The original was darker due to surface oxidation.

In a little time, natural surface oxidation will remove any noticeable differences. One can always hasten the aging process using metal patina acids.

The results were so spectacular that we decided to replace our cabinet hardware with this 19th century reproductions. We were able to create eighteen more knobs from the same silicone mold with no difference in detail.

STEP 1

Assemble your materials. You will need a 1-Pint kit of MoldRite25 and AquaClear resin along with metal powder, mixing cups and mixing stick. You will also need a hot glue gun and a gram scale to weigh out the MoldRite25 silicone rubber.

STEP 2

We placed a small dab of hot glue on the bottom of our part.

STEP 3

The knob was secured to the bottom of a container with the hot glue.

STEP 4

We measured out Part A of the MoldRite 25 using the gram scale. We wanted enough material to cover our knob about 1/2-inch higher than the highest point. Since we were using the same container as our mold box to pour in Part A it was a simple matter of filling the empty container to the same level mark that would equal 1/2-inch above.

STEP 5

In a separate cup we measured out Part B of MoldRite 25 Part B is 1/10 the weight of Part A. We almost forget to account for the weight of the cup. By placing the empty cup on the scale and pressing the ‘tare’ button the scale automatically set itself zero and the weight of the cup was then accounted for. We measured out 10 grams of Part A and 1gram of Part B.

STEP 6

Once Part A and B are measured combine the two parts and mix until you have an even color without any marbling.

STEP 7

After mixing well, we poured the silicone into the mold container in a long narrow stream. We poured in one spot letting the rubber envelope the knob. This drives out more air.

STEP 8

When the mold rubber has set, we sliced open the mold with a razor or X-Acto knife. We cut opposite sides and 2/3rds of the way down.

STEP 9

The mold was spread open like a clam shell to remove the original part.

STEP 10

The mold was baked in the oven at 150-200 F° to outgas any residual alcohol remaining in the mold.

STEP 11

To create a brass casting we needed 325 Mesh brass powder and AquaClear resin along with some cups and mixing sticks.

STEP 12

We measured out equal parts of Part A and Part B in two cups.

STEP 13

 We then spooned out brass powder in a third cup to the same level we measured for Part A and Part B of AquaClear resin.

STEP 14

We added half the brass powder to Part A and the balance to Part B and stirred well.

STEP 15

Part A and Part B are combined in a separate cup and thoroughly mixed before it is poured into the mold.

STEP 16

Once the cast was set, we removed the cast knob and polished it with 0000 steel wool to expose the brass surface.

STEP 17

The duplicated brass knob is on the left.  The original is on the right. The original has a worn lacquer surface which adds to the antique look. In time the newly made copy will gain a patina of its own.