How many of ya'll have gotten caught up in the movement of using a silicone baking mat to spray butane columns directly onto, instead of into a Pyrex dish or similar container?
Many folks have, using it as an alternative to parchment paper, for working their oil into waxes, because it is relatively non stick. It seemed like a questionable practice to me, in view of Cole Palmers and other sites rating silicone rubber as unacceptable for butane service, so I decided to test it myself.
To do so, I solicited an Oil Slick mat from their representative Joshua, and he was nice enough to provide me with one for testing free and provided me with additional information, which I will share with you later in this post.
I conducted the test by carefully weighing the mat and then placing it in a Pyrex dish. Next I sprayed a can of butane directly on it and let it soak in the butane for two minutes, or about the time it took to dissipate the pool of butane. I removed it slightly early, to have an even time.
When I weighed the pad again, I found that it had gained about 30.4% more weight, though even as it sat on the scale, the added weight was evaporating away rapidly. It was more or less like a sponge to the butane.
What that means to me, is that the silicone rubber absorbed the butane.
My concern is that when the butane comes back out, it will bring things with it, which I don't want in my oil.
Interestingly, as it turns out, Oil Slick themselves don't recommend the practice and I've attached a letter from Joshua stating so and exactly why.
I am sure you know, silicone swells in the presence on non-polar solvents. Hexane is actually used as a “swelling agent” for silicone tubing to allow for an easier connection.
The swelling effect is the primary reason why silicone makes a poor compatibility choice when selecting a material to come into prolonged direct contact with non-polars.
As you must also be aware, chemical contamination from “extractables” in silicone materials, (in a procedure such as you are describing) is due almost entirely to the physical release of low molecular weight siloxanes, and other impurities from the manufacturing process.
This is why Tygon 3350, or SaniTech-Ultra, are made with platinum cured silicone rather than the more common peroxide cured variety. This is also why We use platinum catalyzed USP6 silicone in our pads. (rather than peroxide/food grade).
As far as I am aware, we are the ONLY company doing this. The cost of material for a simple “baking mat” would be prohibitive in that industry.
For the record (sometime I feel like a broken record)We do not sell the Pad to spray directly onto. Many (many) folks do, and when we realized it (july of 2012), we switched the silicone we use as our raw material as aprophylactic measure.
We also removed the Logo from our pads, because we feared that immersion in non-polar solvent could act to weaken the bond between that thin layer of logo silicone, and the pad beneath. As concerned as we were about the logo....i cringe when I see folks spraying into parchment. The matrix of silicone in common parchment paper (non-Quilon / silicone coated) is extremely fragile compared to a pad. I imagine the violence of swelling and shrinking on that scale would be tenfold compared to the effect that prompted our own change of material.
The physical wear of swelling/shrinking/swelling/shrinking along with the various stresses inflicted by the innovative public (razor blades, torches etc...) make any sort of performance warranty unmanageable. So we make em as pure as it gets, and when people ask us....we tell em that if they insist on using them this way, to please discard them if they notice any physical degradation.
I would refrain from cutting the pad to perform your testing, as this will expose the inner weave. Once cut or torn, the physical consequences of swelling could lead to damage along the exposed area.
Let me know where to send it, and I will get a Pad out to you today. Always happy to hear your thoughts. I redacted about 2 pages of hyper technical diatribe from this email.... because I figured you have likely done your own research regarding Pt cured silicone, and the various plasticizers that are used in food grade silicone. This is understandably a topic quite close to my heart; and I will be vary happy to discuss at length should you have specific questions (or non-specific musings?).
Also, should you require it, you have my explicit permission to share anything we discuss with whichever forums you are involved in.