The use of super glue in the kiln
causes cyanide gas
This is not true.
But because it is such a persistent belief, a lot of detail is given
below. In short the precautions are:
- use the minimum amount,
- use an organic gas face mask,
- do not wear natural fibres or gloves,
- let the glue cure before placing it in the kiln,
- have the solvents at hand while using the glue.
Super glue
is frequently used as a temporary fixative in assembly of kiln forming
projects. There is some concern about safety, as it is known that super glue is
made from cyanoacrylate, which it is feared will break down in the kiln into
cyanide gas.
Greg Rawls,
a certified industrial hygienist says
"I looked at the MSDSs for several
forms of super glue. The main component is Ethyl 2-cyanoacrylate, which has a
TLV of 0.2 ppm which is relatively toxic. [However,] the thermal decomposition
products are carbon monoxide and carbon dioxide. I did not see a reference to
cyanide gas. However, as I recall cyanide gas dissociates into elemental carbon
and nitrogen at about 800 F. Since you use it in such small quantities, I would
not worry about it. In my opinion the worst thing that could happen is you glue
your fingers to the glass."
Safety issues
To treat the
safety issues seriously and determine if you feel Greg Rawls' view is
justified, you need to look at the issues of toxicity, reactions, adhesion of tissue,
ventilation, first aid and decomposition products in the whole context.
Toxicity
The fumes
from cyanoacrylate are a vaporized form of the cyanoacrylate monomer
that irritate sensitive membranes in the eyes, nose, and throat. They are
immediately polymerized by the moisture in the membranes and become inert.
These risks can be minimized by using cyanoacrylate in well
ventilated areas. About 5% of the population can become sensitized to cyanoacrylate fumes after repeated exposure, resulting in flu-like
symptoms. It may also act as a skin irritant and may cause an allergic skin
reaction. On rare occasions, inhalation may trigger asthma. There is no single
measurement of toxicity for all cyanoacrylate adhesives as there is a wide
variety of adhesives that contain various cyanoacrylate formulations.
The United
States National Toxicology Program and the United Kingdom Health and Safety
Executive have concluded that the use of ethyl cyanoacrylate is safe and that
additional study is unnecessary. 2-octyl cyanoacrylate degrades much more
slowly due to its longer organic backbone that slows the degradation of the
adhesive enough to remain below the threshold of tissue toxicity, so the use of
2-octyl cyanoacrylate for sutures is preferred.
Reaction with cotton
Applying
cyanoacrylate to some materials made of cotton or wool results in a powerful,
rapid exothermic reaction. The heat released may cause serious burns, ignite
the cotton product, or release irritating white smoke. Users should not to wear
cotton or wool clothing, especially cotton gloves, when applying or handling
cyanoacrylates.
Adhesion of the Skin
Various
solvents and de-bonders can be used. These include:
·
Acetone, commonly found in nail polish
remover, is a widely available solvent capable of softening cured cyanoacrylate
·
Nitromethane
·
Dimethyl sulfoxide
·
Methylene chloride
Commercial
de-bonders are also available.
Warnings include:
·
It is a mild irritant to the skin.
·
It is an eye irritant.
·
It bonds skin in seconds.
·
Any skin or eye contact should be
copiously flushed with water and medical attention be sought immediately.
·
Do not attempt to separate eye tissues
– the bond will separate naturally within a few days.
Precautions
·
Use goggles.
·
Do not wear cotton or wool clothing
while using super glue
·
Ventilate the area well. Since
cyanoacrylate vapours are heavier than air, place exhaust intake below work
area. Activated charcoal filters using an acidic charcoal have been found
effective in removing vapours from effluent air so the bench top air filters
are suitable for use while using super glue.
·
Avoid use of excess adhesive. Excess
adhesive outside of bond area will increase level of vapours.
·
Assemble parts as quickly as
possible. Long open times will increase level of vapours.
Evaporation Effects
·
The effects of heating cyanoacrylate
are not completely known. The flash point is known to be greater than 85ºC. As
a precaution do not remain in the area of the kiln after that temperature has
been reached.
·
The decomposition products
are carbon monoxide and carbon dioxide. There is no reference in the
literature to cyanide gas. It is highly unlikely that heat will cause the
release of cyanide gas at any time during the heating. To be certain, you
should make sure the evaporation of the glue is complete before firing the
kiln.
See this tip
for the use of super glue in kiln forming. http://glasstips.blogspot.co.uk/2013/12/super-glue.html
