September 21, 2017

Lifecasting field notes- M&K wax for sprues+gates

Experiments and notes by Naomi Rosenkranz and Hannah Elmer

See also video and photos by Lan Li

When making a mold to cast from life, a sprue and gate system is required to create 1) where the metal will be poured into the mold, 2) channels/leads for the metal to flow to the specimen, and 3) vents from the specimen that allow air and excess metal to flow out of the mold during the metal pour.

The material used to make the elements of the system should be malleable while preparing and posing the specimen, withstand the plaster pour, and leave the mold during burnout to create empty channels.

This technique is related to the lost-wax casting process (link to Encyclopaedia Britannica definition) still used today.

Another quick reference about this process is the book "Lost-Wax Casting: Old, New, and Inexpensive Methods" by Fred R. Sias, Jr. - see pdf of Chapter 5: Placing Sprues

For the September 2017 M&K lifecasting experiments, we used two types of wax for all mold gates and some sprues/vents.

1. Modern purchased wax sprues:

2. A wax composition we made and formed ourselves -- "M&K wax"

Experimental planning

We based our recipe on a recommendation from sculptor/scholar (and former M&K expert maker) Andrew Lacey. His recipe emailed to Pamela of "25% amber rosin to beeswax" made it unclear to us whether he meant:

1. [25% = 1/4 part] rosin to [1 part] beeswax --> 1x rosin + 4x beeswax

   1. This means the total composition is 5 parts: [1/5 = 20%] rosin and [4/5 = 80%] beeswax

OR

2. [25% = 1/4] rosin to [75% = 3/4] beeswax --> 1x rosin + 3x beeswax

   1. This means the total composition is 4 parts: [1/4 = 25%] rosin and [3/4 = 75%] beeswax

This was one uncertainty/variable for this process. Other variables include: whether the material parts are measured by weight or volume, how the composition is brought together and heated, how long to heat the mixture, and how it should be cooled. Another important variable is the addition (and quantity) of a colorant and/or clay-like earth pigment (such as venice/venetian red), a common part of the recipe according to Lacey and Pamela's research and experience. In theory, this additive can help simply color the wax+rosin for better visibility and also alter the texture and malleability properties.

We decided to do the following:

• The second interpretation of Lacey's recipe might seem more plausible and so we would first test a composition of 1:3 rosin to wax.

• As the gum rosin we have in the lab is in uneven chunks about the size of US nickel to quarter, we decided it would be easier to measure by weight rather than volume. For this type of process, measuring by weight rather than volume also seemed more plausible and so we would try this first.

• After this initial trial, Pamela could then advise on the final texture and adjustments to the process could be made in subsequent trials.

• Once we settled on the composition, we would introduce venice red in another trial and test the quantity needed.

Basic recipe

Materials

• Beeswax, 100%, yellow (Nature's Oil)

  • Melting point: 63 °C

  • Flash point: 205 °C

• Gum rosin (Diamond G Forest Products)

  • Diamond G does not provide SDS information, but states the rosin is derived from Pinus elliottii

  • From a quick search, it appears that the closest characterization is CAS 8050-09-7 (like to MSDS)

    • Melting point: 100-150 °C

    • Flash point: 188 °C

• Venice/venetian red (Kremer #40510)

• Water for bain-marie

Equipment

• Scale

• Mason jar

• Cooking pot large enough to fit the mason jar

• Hotplate

• Stirring tool (e.g. chopstick)

• Heat resistant gloves

• Marble slab

• Palette knife

Procedure

• Weigh out materials

• Combine the rosin and beeswax in the mason jar

• Create a bain-marie: heat the mason jar inside the pot on the hotplate filled with enough water to reach above the volume of the beeswax and rosin in the jar

• Heat the mixture until the wax and rosin have melted and become homogenous, stirring as needed

• If adding the venice red, stir it in

• Cool the mixture slightly outside of the bain-marie before pouring out the mixture onto the marble slab

• As the mixture cools and hardens, use hands and palette knife to peel the wax/rosin off of the marble

• HANDLING TIP: Slightly moisten the marble slab and hands for ease of handling the sticky mixture

Field notes

Trial 1 - Wax and rosin only, measured by weight

Ratio

1 part rosin

3 parts beeswax

Materials

11g rosin

33g wax

• Rosin and wax were measured

• Due to unfamiliarity with rosin and its lower flash point, the wax was added to the mason jar first and then added the rosin on top (further away from direct heat)

• A steel pot was set on a hotplate inside the fumehood to boil enough water to cover the volume of the materials inside jar

• Turned the hotplate down so that water was at a simmer before adding the jar. Because the jar was so light, it had to be held in the water by hand (using gloves) so it would not flip over in the water. We also added a second jar filled with rocks to the pot to help the water level rise and to help prevent the other jar from flipping by reducing the space inside the pot

• 1:40pm - jar with rosin and wax goes into water. Stirring with chopstick

• 1:46pm - wax melted but rosin is not. Rosin is a little soft

• 1:51pm - temperature taken with IR thermometer: 95.5 °C

• ~1:57pm - removed from heat and cooled slightly on a small towel on lab bench

• 2:04pm - temperature taken with IR thermometer: 74 °C

• 2:05pm - poured onto marble

  • Solidified within ~30sec max

  • Used combination of hands, chopstick, and palette knives to scrape the solidified mixture on the slab and in the jar

  • Quite sticky, pale yellow in color. Leaves a slight residue on hands

Trial 2 - Wax and rosin and venice red, measured by weight

Use same ratio of rosin and wax:

1 part rosin

3 parts beeswax

Upon recommendation from Pamela, we decide to conduct a trial with the addition of 1 teaspoon by volume of venice red. Because we don't know exactly how much venice red will be an appropriate amount and what exactly we are looking for in the final product, we decide to add this recommended amount slowly - start with about ½ and then continue to add the rest of the 1 tsp incrementally until the final product seems similar to what Pamela has made in the past.

We measure the weight of 1 tsp of venice red so that all ingredients are measured in the same way. This will also allow us to weigh any venice red not mixed into the wax/rosin and calculate how much has been added.

Materials

11g rosin

33g wax

1 teaspoon = 5g venice red (NOTE: not all of this was used. Please see the end of the field notes for the amount actually added to the mixture and for subsequent ratio calculations)

• It is decided that the venice red should be added after the wax and rosin have melted and become homogenous, rather than adding all ingredients at the beginning, as this seemed to us that it would allow the venice red to be better integrated and help us decide how much is needed as we add it incrementally.

• 1 teaspoon by volume of venice red (using the lab's metal measuring spoons) is measured in grams:

  • 1 teaspoon = 5g venice red

• The same jar as Trial 1 is used without cleaning (there is a thin layer of the previous mixture still stuck to the sides of the jar - as we are using the same proportions, this seems negligible for the trials here)

• As the rosin took longer to melt than the wax in the previous trial, we use smaller pieces of rosin and add them into the jar first followed by the wax on top.

• The same procedure as Trial 1 is followed for the melting

• 2:23pm - Jar with wax and rosin goes into the bain-marie

• 2:33pm - The rosin/wax mixture is completely melted and homogeneous. Approximately 1/3 of the measured venice red is added to the jar and incorporated into the mixture.

• To test the effect of this addition on the color and texture, we use the chopstick to drop a small amount of the mixture into a plastic container to cool and test by hand. The mixture is a light red, slightly more opaque than the wax/rosin only mix but still quite transparent, and similar in texture and stickiness to the wax/rosin only mix:

(drops smeared onto notebook paper)

• Because it is still quite similar to the wax/rosin only mix, it is decided that more venice red should be added.

• Approximately 1/3 tsp is added to the sample, integrated, and a few drops cooled as before. The mixture is stronger in color, more opaque, and less sticky yet still easily malleable than before:

(drops smeared onto notebook paper)

• This mixture is similar to Pamela's previous samples and it is decided that no more venice red is needed

• 2:37pm - temperature taken with IR thermometer: 93.5 °C. Removed from heat and cooling process followed as in Trial 1

• 2:39pm - mixture is poured onto marble - less cooling time in jar than Trial 1 to allow for better removal from jar

• We measure the remaining venice red not added to the mixture, which totals 1.1g

  • This means that 3.9g venice red was added to the mixture

• Final recipe and ratios:

  • By weight

    • 11g rosin

    • 33g wax

    • 3.9g venice red

  • Ratio

    • 1 part rosin

    • 3 parts wax

    • 0.35 part venice red

  • Percentage

    • (Total = 11+33+3.9 = 47.9; percentage determined by dividing each part by this total)

    • 22.96% rosin

    • 68.89% wax

    • 8.14% venice red

    • (Note: due to rounding to two decimal places, the percentage total is 99.99%. Rounding to three places is 100.01%)

Use of M&K wax

Both the products from Trial 1 (wax/rosin only) and Trial 2 (wax/rosin + venice red) are used for the lifecasting experiments undertaken by M&K on Sep 21 and 22, 2017.

All gates for these molds are made from this wax, while a combination of M&K wax and the purchased sprues are used for the sprues and vents.