Lab Notes
Jef Palframan & Emily Boyd
Tuesday, 11/18/14, 9:23am, outside temperature 27 degrees F.
Columbia U Chemistry Lab
Recreating “To make a very beautiful gold color”

We are attempting “To make a very beautiful gold color” today with four types of oranges.

Jef has procured three types of oranges: organic Valencia oranges from “Real Organics” orchard, the location of which cannot be determined; unspecified not organic navel oranges; and not organic tangerines from Heller Bros. Orchards, Winter Garden, Florida, USA.

Our first conundrum is to figure out what is meant by “a cellar or…a wet place” in which the recipe specifies the pigment should be stored for 8-10 days. We are figuring that a cellar would be around 50-60 degrees, but room temperature at the lab is 72 degrees, and the fridge does not have a thermometer but is likely colder than that.

We decided to store the beakers that the zest/sulfur mix will be placed in, inside a bowl filled with a layer of water, sealed with plastic wrap and placed inside our lab fridge, whose temperature we will regulate to be warmer than freezing.

TANGERINE
We started with the tangerine because it has the brightest color. We used a knife to “zest” two tangerines, yielding what appeared to be about 2-3 tablespoons of tangerine peel. Further, we used the knife to remove as much of the traces of pith as possible, as the recipe specifies that the peel should be removed from the white of the orange. We placed ½ of this quantity in a marble mortar and pestle. Attempting to grind the pieces as is was difficult because they proved slippery, so we used a scissor to cut them down to a more manageable size, and then ground them for approximately 15 minutes, until the zest looked well ground, and was beginning to turn into a paste. We then brought the mortar over to one of the vented hoods, and measured the quantity of zest which we had ground – it was approximately 2 teaspoons. To this, we added (as specified by the recipe), an equal quantity of sulfur: 2 teaspoons.

Jef ground the zest together with the sulfur for approximately 5 minutes. We noted that with the addition of the dry sulfur powder, the mixture was less slippery, and hence easier to grind in the mortar. After about 5 minutes, the mixture seemed well pulverized and ground together. All of the larger pieces of zest had pretty much disappeared into a uniform mixture.

VALENCIA
Valencia oranges are the type Jef has judged are closest to the type of oranges that we hypothesize would have been sourced by our maker in EM France. We “zested” the oranges in the same way, cutting away as much of the pith as possible, and cut the pieces with a scissor before grinding them in the mortar. Emily observed that it was easier to grind these peels than the tangerine peels had been, and thought it was due to the quality of the peels. Jef thought it was because we did a more efficient job of cutting the peels with a scissor before they made it into the mortar.

Because the Valencia oranges were somewhat larger than the tangerines, they made more peel, so we had three teaspoons or peel-paste to which to add three teaspoons of sulfur. This mixture proved more difficult to mix together, likely because there was simply a greater quantity of it in our mortar, decreasing the surface area that was possible to grind at one time. It also may have been more difficult because Emily began the grinding process, and she is less physically strong than Jef. Once Jef took over the grinding, the mixture quickly evened out.

NAVEL
With the Navel oranges, the zest separated most easily from the pith, likely because the rind was quite thick. They ground very easily into the peel-paste, and we created three teaspoons of the paste, so we added three teaspoons of sulfur. Emily ground this mixture together for quite some time, but it proved difficult to get the zest to mix in with the sulfur as readily as when Jef had been grinding the other mixtures. Once Jef took over, he made speedy work of getting the mixture to completely intermingle.

All three versions were poured into small beakers.

Joel, observing our process, mentioned that really what we are doing is getting the zest to break down to orange oil, which is acting as a binding agent for the pigment.