Stencil Science: Hand Drawn Stencils

November 30, 2016

Its winter now in the continental US, which means now is a very good time for us to do a quick refresher on how climate impacts tattoo stencils.

Those of you who have been reading here for a while probably remember our blog post about stencil paper- we talked a lot about what precisely stencil paper is and how stencils should be produced using S8’s tattoo stencil paper. We highlighted 2 major variables in stencil production in that article- which we’ll recap here and expound upon- that tattooers should keep in mind when producing stencils using any stencil paper.

First, a recap: S8 RED Stencil Paper features a wax emulsion with a colorant suspended in it. Think “crayon.” Like crayons, stencil papers respond to heat- by warming the wax blend, we are able to selectively transfer it from the backing sheet to the stencil paper. Thus, the most important variable is heat.

Heat is a movie starring Al Pacino and Robert De Niro, but it is also a way of describing energy. Heat either radiates or conducts (or both), and flows from hot to cold. Thermofax printers, and other thermographic printing machines, utilize the interconnected relationship between optics and thermodynamics to selectively heat sections of the wax emulsion. You can read all about how thermographic printers work here.

But suppose an artist chooses not to use a Thermofax or doesn’t have access to one. Without the tremendous amounts of energy transferred inside a thermofax, the artist is now faced with a quandary- how do they selectively mobilize sections of the wax emulsion? Of course, in practical terms, we know the answer: “trace.” But what is going on when the artist traces?

Without getting too deep into thermodynamics, the artist is transferring energy into their surroundings when they trace on a piece of stencil paper, and it is this energy that mechanically and thermally changing the wax emulsion. Recall our conversation about coefficient of drag, when we highlighted some of the places where the mechanical action may generate large amounts of heat. This heat is not being “poofed” into existence- thermodynamics reminds us that energy can neither be created nor destroyed. Instead, physicists recognize that motion and heat are interchangeable insofar as they require the same amount of work. For example, the heat that we experience when we rub our hands together is a simply a conversion of the heat of that motion.

Similarly, when an artist traces, they are mechanically inputting energy at the point of contact between their pen and the stencil paper. Because the waxes that we use exhibit high levels of plasticity when ambient temperatures are in the upper 70s and above, and because the melt point of our waxes is relatively low, the heat generated by the mechanical work of tracing and the pressure exerted transfers the wax from the backing paper to the stencil paper. However, as the ambient temperature decreases, the wax becomes more brittle. Brittle waxes result in poor stencils. This means that the first big bit of advice is to ensure that the ambient temperatures are fairly warm- the “zeroth law of thermodynamics” suggests in part that all systems tend toward thermal equilibrium when linked by a wall permeable only to heat and they do not change over time.

In laymen terms, that means that if you leave your stencil paper in your car over night and the outside temperature drops into the 40s, the stencil paper will have an internal temperature in the 40s the next morning. Keeping the ambient temperature in your shop warm is probably more of a priority to facilitate client comfort during winter months, but it definitely helps ensure that when you hand trace a stencil that the wax is sufficiently pliable.

But lets say that you don’t want to keep your shop perpetually at 80F. What can you do to ensure that when you trace a stencil you get optimum outcomes? Well, locally inputting heat definitely helps. Some tattooers have found that a hair dryer on low temperature can warm waxes up quickly and evenly, and so we always recommend that artists who find themselves with stencils that appear to light try one out. Similarly, placing the back of the backing sheet onto a light table that utilizes incandescent bulbs is another way some artists have found success, though the heat output on LED bulbs is too low to impact heat gain.

The other major variable to keep in mind is humidity. As we’ve said before, water vapor is a selective absorbed of infrared energy and locks fairly large amounts of heat in the atmosphere. Dry air is a poor insulator- think of how cold deserts can become at night- which means that ambient temperatures can fluctuate more actively in dry climates. Inside the tattoo studio, this is most apparent under air vents. Tattooers that hand trace under air vents will likely find slightly reduced outcomes than they would expect elsewhere in this shop. The easiest way to control for this is to relocate where artists from dehumidifying spaces, or to artificially increase the relative humidity of the shop via a humidifier.

This blog has gotten quite long, so we’ll leave it off here for now. Be sure to leave us questions and comments below.



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