Tag Archives: vapor

Pure Smoke

This was making the rounds on email yesterday: The Pure Smoke system by Jason Brumbalow. Say you need a clothes iron or a tea kettle to make steam on stage, but generating that kind of heat is too dangerous for the actors. You can probably hide one of these somewhere and let it make some room-temperature theatrical fog for you.

It essentially works like an e-cigarette with a nicotine-free cartridge. The major difference is you cue the vapor with a squeezable trigger rather than an airflow sensor which is activated when you inhale on the end. The vapor is generated from propylene glycol, which is among the safer kinds of chemicals used in theatrical foggers and electronic cigarettes. 1

The website lists the system at $147, with refill smoke packs starting at around $25. It says each cartridge gives you over 80 large “puffs”, with a refill pack giving you 10 cartridges, so that’s about 3 cents per puff. The cost is a great deal cheaper than palm-sized theatrical foggers ($1850), though I’d imagine the vapor is considerably less dense and long-lasting.

It has a battery pack which takes 4 AA batteries (not included) which is connected through a long wire to a squeezable trigger mechanism. The mechanism is rigged to be strapped to a performer’s chest, though I imagine you can alter it to fit any prop you need the smoke in. A hose runs from the mechanism to the dispenser tip, which also holds the smoke cartridge. The dispenser is about 3 1/2″ long; the diameter of the base is about half an inch, and the tip is a quarter of an inch.


  1. The amount of vapor produced by the Pure Smoke in the video looks to be extremely small, but if you are interested in the possible health risks of inhaling propylene glycol, especially in the quantities produced by full-stage theatrical foggers, I urge you to check this fact sheet about propylene glycol from Monona Rossol, the leading expert on chemical hazards in the entertainment industry.



What is Celastic?

Celastic advertisement
originally uploaded by Trimper's Haunted House Online

Celastic was first trademarked in 1926. It was being used by the theatrical industry as early as the 1930s, and saw its most widespread use in theatres of all sizes by the 1950s. It appears to be one of the most popular prop-making materials of the ’70s and ’80s, and why not? It was used to make everything from masks to armor, statues to helmets. It reinforced other props, or simply gave them a smooth, flowing surface.

Celastic is a plastic-impregnated fabric which is softened with a solvent such as acetone or MEK. When it is soft, it can be manipulated into nearly any shape; it can be wrapped around forms, pushed into molds, or draped over statutes. You can cut it into strips or small pieces; Celastic adheres to itself. When it dries, it becomes hard again, thus retaining whatever shape you can manipulate it into. If necessary, it can be resoftened and further manipulated.

Here is an example of what passed for safety knowledge back when the use of Celastic was prevalent: “Rubber gloves should be used to keep the Softener off the hands. The liquid is not injurious under normal working conditions… Common-sense precautions will make the medium acceptable for any school use” (Here’s How by Herbert V. Hake, 1958). Of course, “not injurious” is not the same as “harmless”.

Acetone and MEK of course can be absorbed through the skin, and the fumes can cause neurological damage. As prop makers became more health-conscious and aware of the effects that cumulative exposure to solvents, especially strong ones like MEK, could have on their bodies, they began seeking out alternatives and scaling back the use of Celastic. Today, you’d be hard-pressed to find even a single practitioner using this material. You find one occasionally; their argument is that no other material can be draped as finely as Celastic, and if you take the proper precautions, you can protect yourself. There is some point to that; all chemicals can harm your body to some extent, and you need to be aware of how that chemical can enter your body, how much is entering it, and how to properly limit your exposure to it. If you wear the proper gloves and sleeves, respirator, goggles and face shield, and work with the solvents in a well-ventilated area (preferably some kind of spray booth or hood), working with Celastic would be no more dangerous than working with wood.

Of course, we rarely work alone in theatre; if one person is working with Celastic, than everyone is breathing the fumes. Prop shops are rarely the best ventilated areas, so the vapors can hang around long after everyone has removed their respirators. And of course with all the deadlines and time pressures, the temptation to take shortcuts in safety are always present; “I’ll just dip this one piece in Celastic really quickly; I don’t need to go all the way to my locker to get my respirator.”

Most prop shops these days seek to use the “least toxic alternative.” Whatever perceived benefits Celastic may have is far outweighed by the existence of less toxic materials that will accomplish the same goals.

Some of these alternatives are thermoform plastics which are softened by mild heat; they can be dipped in boiling water or blown with a hot air gun. One of the first to be introduced was known as Hexcelite; it was developed as an alternative to plaster for setting broken bones in a cast. Today, it is sold under the trade name of Varaform. Two other popular brands are Wonderflex and Fosshape. Wonderflex is a hard plastic sheet, while Fosshape is more of a plastic-impregnated fabric.

Breathe Nothing But Air

A visual comparison of healthy versus harmful gases.
A visual comparison of healthy versus harmful gases.

My father is a potter, and his job includes all sorts of dangers to the lungs, such as dust from dry clay, mist from spraying glazes, and fumes from firing pots. His words of wisdom for dealing with all this safely are “breathe nothing but air.” Putting these simple words into practice can be a bit more complicated, however.

Proper ventilation is a must when working in almost every aspect of prop-making: wood-working, welding, molding and casting, painting, etc. You can (and should) supplement it with more specific safety measures, such as respirators and dust collection systems, when necessary, but overall ventilation is still the backbone of any healthy prop shop. Without ventilation, you will be putting other workers and visitors to your shop at risk. Also, many harmful particles remain in the air for a long period of time, well after you’ve completed your task and removed your respirator.

It’s helpful to know the different kinds of harmful substances that may enter your lungs, as this will determine what kind of protection you need. I learned about the various physical forms a chemical can take while working at the Santa Fe Opera, which has a great safety training program:

Solid, liquid, fume, dust, mist, gas, vapor.

I would hope you know what a solid and a liquid are; the other forms may require some explanation. It is important to know the difference between them because they determine what kind of protection you need to keep them out of your lungs. Wearing a dust mask to protect against vapors, such as those found in spray paint, is not only useless, but can even be more harmful than wearing nothing. Why? When wearing any kind of mask or respirator, your lungs need to work harder to pull in enough air to breathe, so wearing the wrong kind of mask will make your lungs suck in more spray paint than when your breathing rate is lower.

When a solid is heated to its melting point, it may release a fume, which is a solid particle suspended in the air. Welding and soldering are common practices which create fumes.

Sanding, grinding and even just handling powders can create dust. Like fumes, these are solid particles floating in the air. Though most dust is trapped by your nose hairs, some dust is so fine it can make it all the way to your lungs; these are known as “respirable” dusts, and are the most harmful. Some are so fine they are invisible.

Tiny liquid droplets in the air are known as a mist. You can create mists from spraying liquid, or from boiling it. Some mists may even carry solid particles inside.

A gas is the third phase of matter, after solid and liquid. Normally, when we talk about what form a certain material comes in, we talk about what phase it is at room temperature. Common gases used in the props shop can include argon and carbon dioxide for welding, and acetylene and propane for torches.

When a liquid evaporates, it becomes a vapor (notice how “vapor” appears in the word “evaporate”). Evaporation can be sped up by heat. Vapors are molecules just like gases, and the only real difference between the two are that vapors can re-condense to a liquid or solid in a high enough concentration.

You’ll notice the first three forms–fume, dust and mist–are all particles of some sort. You can filter particles with a physical barrier, such as those found in NIOSH-approved disposable respirators (sometimes referred to as “dust masks”).

Gases and vapors are molecules and cannot be physically filtered. A barrier which keeps molecules of harmful gas from passing through will also keep molecules of oxygen from passing through, and you kind of need oxygen to live. In these cases, you need a respirator with a chemical cartridge. A chemical cartridge will either capture and hold the harmful molecules or chemically react to transform them into something less harmful. One of the earliest substances to be used in this manner is activated charcoal, which is still relied upon for filtering many kinds of chemicals. Your Brita filter uses activated charcoal to filter your tap water.

There is no single type of chemical respirator cartridge which will filter out every kind of gas or vapor found in prop making. It is absolutely vital that you know and understand what kinds of chemicals you are working with and what physical forms they are in so you can choose the correct type of respirator and cartridge to wear. As with particles, wearing a respirator makes your lungs take bigger and deeper breaths to compensate for the reduced flow of oxygen; wearing the wrong kind of respirator means you are taking bigger and deeper breaths of a toxic substance than you would wearing nothing. Some chemicals cannot be filtered by any type of cartridge and require either a supplied-air or self-contained breathing apparatus.

In any case, proper ventilation in your shop is still your best defense against airborne chemicals.