Making A Bronze Base

Thank you for taking the time to read this. I don’t know if this information will help anyone, but I always tell myself, “You don’t know what you can or can not do until you try”.

Ernest Bleeker

The Lost Wax Method
By Ernest W. Bleecker

This endeavor was all new to me and I don’t claim to know the exact way to do it, but, after reading up on the construction of a mold and searching the internet to find information on “lost wax”, I used my knowledge of carpentry and skills as a machinist - plus a lot of trial and error, to make my own base. The base would be used to hold the Venetian shade that I had previously constructed and given to my friend, Kathy.

The first step for Kathy and me was to think out exactly what we wanted to accomplish as far as style and color. After finding pictures of what we wanted to interpret, I began by drawing and gathering materials for the model. I used Bass Wood - the finest wood that is available for carving. (You can purchase wood such as this at specialty wood lumber yards.) After purchasing the wood, I glued it together to form the shapes I wanted.

Next, I put the shapes in a lathe and turned them down to the sizes that I calculated I would need for the finished base. Once I machined them to size, I assembled all the pieces so that I’d have the rough figure of the base.

Now, the hard part was laying out the design around the different levels. To me, a big help was being able to refer to Dr. Egon Neustadt’s book, The Lamps of Tiffany. The base, that I wanted to reproduce, was described layer by layer in this fine reference book and the photos helped me plan out the designs that were needed at each level.

Finally, I was able to begin carving. After many hours and a great deal of patience, the carving was finished. I was relieved and proud of my accomplishment.

I took my finished model apart and got it ready to make the molds. There was a total of eight molds; seven for the base and one mold for the heat cap. The reason there had to be so many molds is because I needed to be able to get inside some of the parts to do the work. An example of this is the bottom layer. I wanted this layer cast nearly solid so that it could support its heavy shade without tipping over. The second part needed to hold a dimmer switch inside it. The next three pieces could have been cast as one, but it was easier to make them in separate parts. The top level had to be made into two parts because of all the filigree work that was needed. This level had to be cast hollow. (Some of Tiffany’s bases have filigree on every level, but mine was a reproduction of a base at the New York Historical Society that had filigree only on its top portion and on the heat cap.)

To make the molds, I used mold material purchased from the Polytek Development Corporation – located in Easton, Pennsylvania. This company was very helpful and was happy to give me recommendations for the best products to use in this project. Their website www.polytek.com proved to be extremely informative.

Most of the molds were made in halves. The only one piece mold was the top level of the base. Even the mold for the heat cap was in two pieces. At this point, common sense comes into play: you have to figure out where air might get trapped and make provisions for venting it.

The bottom row shows the model carving.

The dark brown pieces are the waxes. (A special casting wax was used for this process so that, as this wax melts out, it doesn’t leave any oils behind that might ruin the bronze.) The back row shows the molds. If you look closely, you’ll be able to see the details in the yellowish-colored rubber molds. (The molds started out as white rubber, but the heat of the wax discolored them.) The white plaster casts that you see in the photo are used to keep the rubber in shape. Actually, you can pour the rubber thickly, but the cost, about $125 for a half gallon for a two part mix. is prohibitive.

After I was satisfied with the way the waxes came out, I shopped around to find a foundry to do the casting. I brought along the wood model so they could give me a price. (I brought them the waxes too, but didn’t give up my molds!) After making a decision about which foundry to use and realizing how much it would cost, I took the castings home to refine and carve them.

The foundry took the waxes and put wax spouts and vents – called sprues, onto the model so that they can pour the bronze. Once this is prepared, they make a silicone mold of each wax model. Each piece is dipped ten times in a special mix that will take the high heat of the bronze. (After each dip, it takes a day for each piece to dry so, in all, this step alone took ten days.) Once this step is completed, the molds are laid upside down in an over so that the wax can melt out. After the molds are removed from the oven, they are ready to be cast. The casting mold is kept hot so that the molds don’t crack as the bronze is poured. After cooling, the silica shell is broken away, the sprues are cut off and it is sandblasted.

I took my model home to “clean” it up. I re-carved some of the design and did more metal tooling on the filigree. Once the base was cleaned and wire-brushed, I heated the piece so that it would “take” the patina and proceeded to color it. After we were satisfied with the patina, I wired it and installed the dimmer and sockets. I applied a clear wax to protect the patina and glued some felt to the bottom of the base so that it wouldn’t scratch the table’s surface. At long last, I was able to give Kathy her gift!