Innovation, renewal are powerful motors in the vaping sector, they boost the sales of products and also respond to safety concerns. Heating elements are probably the part of vaping devices where most of the fantasy is expressed. Kanthal, Nichrome, twisted, Clapton wires… all type of alloys with different shapes are being experienced but one type of coil has no filiation with others: the ceramic coil.
What is ceramic?
Ceramic has reached every little part of everyday’s life, why not in your e-cigarette?
Exit the old fashion pottery, bricks and tiles, most of them in ceramic. Modern ceramic is used for tooth replacements and dental prosthesis, to make the blades of kitchen knives and for many other types of applications. Ceramic parts can be remarkable for their mechanical properties (resistance to abrasion, elasticity, tolerance to high temperature), optical properties (from transparent to completely opaque) and electrical properties.
In coil science, the lack of a protective bonded coating results in frequent failures of the wires since oxidation of the alloy is accelerated at elevated temperature. The phenomenon is amplified in the presence of aggressive mixtures of e-liquids and during repetitive heating and cooling periods. It results in producing a layer of oxidized material at the surface of the wire. The risk for that layer to peel off and for particles to be released is present, definitely.
The different types of ceramic coils
Some manufacturers have already included the “ceramic” in their atomizers, but confusion persists with regard to which type of ceramic is being used. Together with ceramic, the brands announce a longer life, self cleaning properties, absence of dry hit and a better rendering of flavors. They also put forward the absence of metallic parts that oxidize in presence of e-liquid and a safer option for the user.
The ceramic used for heating elements is basically a mixture of the oxides: lead, silicon, boron, magnesium, titanium and one or more oxides selected from the group consisting of the oxides of nickel, manganese, cobalt and iron. The ceramic is further fused to bond to the wire and forms a protective glaze that prevents further oxidation. The oxides contained in the mixture are firmly trapped in the structure and and contribute to the electrical properties. The patents for coating wires have been registered in the early 1960s and are such techniques are still employed nowadays.
Another type consists in a microporous ceramic, a cylinder molded around a resistive wire. Here, the material used is Silicium and the ceramic is nothing less than glass.
Vaporesso, for example, proposes the cCELL and describe it as “a revolutionary heating element”. Pretty similar in the Stainless Steel Organic Cotton Coil (SSOCC) family, a microporous ceramic coil by Kanger.
Guo promote their “revolutionary” CVU Chip, the combination of a resistive wire coated with a piece of ceramic (the chip), around which is wrapped a cotton wick. The Razor Chip in the Vaping Outlaws’ Para Tank resembles Guo’s CVU Chip.
Is the ceramic as ideal as claimed by the manufacturers?
Manufacturers claim ceramic coils are made to withstand very high temperatures without emitting chemicals, to last much longer than the common one-week disposable metallic resistive wire. But the concern is more physical. It consists in the degradation of the ceramic and the possible inhalation of ceramic powder that flakes off.
Vaporesso’s cCELL ceramic coil is presented as a microporous ceramic tube coated with cotton in which runs a resistive wire. When delivering power to the wire, it heats up the ceramic all around. The ceramic element itself is a wick; because of its microporous structure the juice climbs by capillarity. The bigger surface area of a microporous material contributes to enhance the taste in the aerosol compared to wicked wires. The absence of contact between the red wire and the liquid also prevents spit-backs, according to the manufacturer.
Professionals are sceptical
As early as January 2016, Phil Busardo was concerned with potential material release in vapor when reviewing Vaporesso’s ceramic coils. The famous reviewer mandated a third party for further analysis of the particles emitted during vaping with such a microporous ceramic coil. The report of analysis did not confirm Phil’s concerns and concluded that no particulate matter could be found after using the ceramic coil.
More recently, Uwell, a Chinese manufacturer, carried out visual inspection under the microscope of different ceramic coils from three concurrent brands and concluded in a potential for hazardous particle emission. The company points out that ceramic powder released in operation can cause cancer.
Shenzhen Uwell Technology Co., Ltd is a young company established in Guangdong, China. Their main activities are quality control, safety management and improved technology of electronic cigarettes. Part of Uwell Hong Kong, a major electronic cigarettes manufacturer, Shenzhen Uwell commit to provide best electronic cigarettes with moderate prices, and professional services for customers.
Uwell finds porous ceramic harmful
Far away from a conspicuous scientific approach, Uwell’s “analysis” rather consists in a compilation of microscopic observations with author’s comments on potential harmfulness. Irrespective of the author’s considerations, the document brings some interesting aspects of microporous ceramic heating elements.
Visual inspection addresses the presence of cotton around the ceramic heating body. It also addresses more specifically the microporous structure: the ceramic coil appears as a glasslike surface where impurities are embedded. When broken, the glasslike parts have defects and sharp edges. The size of the ceramic powder is “distributed between 30-120 micrometers which is too tiny to be seen by the human eye”, reads the document.
According to the author, the powder comes from the molding of the ceramic coil itself. In order to produce a porous ceramic material the manufacturer bakes together raw materials such as silica powders and pore-forming materials like starch or other organic polymers and pores are formed while the pore-forming agent combusts and escapes. Firstly, this process makes the ceramic brittle and fragile in case of shocks. Secondly, vaporization of e-liquid may expand and damage porous ceramic material, making it more friable.
From a medical aspect, the inhalation and retention of inert material in the parenchymal tissue of the lungs may lead to chronic infections like fibrosis (the author refers to silicosis, but one can also cite asbestosis). This is the main danger upon exposure, as presented by Uwell with regard to their conclusions.
Which ceramic coil is best for vaping?
If the objective of using a ceramic coil is to increase its longevity, a wire glazed with ceramic will be preferable. The counterpart is its price, generally one order of magnitude higher than the cheaper porous ceramic. Note that this one doesn’t exclude the use of a wick. An inconvenient? – not really. Changing the wick offers an opportunity to inspect visually the heating element to make sure that no “caramel” (the combustion product of organic molecules at the origine of the production of acrolein, for example) sticks inside the heating element.
If the rendering of flavor is sought, the microporous ceramic heating bodies are a right choice, for a price generally below $20. A major drawback is that they may become friable and release particulate matter when ageing of if they are shocked. The theory that such particulate matter may accumulate in the lungs and create fibrosis is likely an extreme case but definitely not what you expect from your e-cigarette. Here, the quality of the ceramic is the main factor of the risk: the more porous, the better the taste, but also the more brittle.
Finally, new products are emerging like coil-less solutions for atomizers, half way between ceramic-glazed wires and the metal alloy. It is the case of the Yihi’s SX Pure whose longevity exceeds 2 months, according the manufacturer, for an intermediate price between microporous and glazed wires. The tolerance of such a coil-less heating element to high temperature allows pyrolysis and self-cleaning properties, according to its manufacturer.
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