Glue in Kilnforming

 

There is some general guidance on using glue in kiln forming processes.

Avoid Glue Altogether

Do not use glue of any kind if at all possible. First look at other ways of stabilising the pieces. You can place clear frit or powder around or under the unstable pieces. Of course, if you are firing to less than a contour fuse, this will show. If the pieces are rolling, you can grind a flat spot to keep them stable.

Use Minimum Amounts

Use as little as possible if there is no other way to stabilise the pieces until you get them to the kiln. Use weak glues. Dilute the glues if water based. Place only a small dot of glue at one place.

Use Care in Placing

Place the glue at the edge of the glass pieces, not underneath. This allows the glue to burn out cleanly. Placed in the centre, the glue burnout is trapped under the middle of the glass. This leaves a black mark or a big bubble.

Avoid Glue with Additives

Use no glue containing additives. Many of these additives will remain after the adhesive part of the glue has burned off. These will promote devitrification.

Some Popular Glues

PVA also known as wood glue, white glue, carpenter's glue, school glue, Elmer's glue in the US, or PVA glue. This boils at 112°C/234°F.

         

Super glue and other cyanoacrylate glues have a boiling point 54-56°C (129-133°F).

Lacquer and hair spray have boiling points around 189°C/372°F)

Aloe vera gel has an ignition point of about 232°C/450°F. So, its boiling point is even lower than CMC.

CMC (carboxymethyl cellulose) includes wallpaper paste, Vitragel and most fusing glues. These have boiling points around 260°C –270°C (500°F –518°F).

Xanthan gum is a thickener sometimes used as a kilnforming glue. It boils at 311°C/592°F.

Proprietary kilnforming glues are generally without additives and diluted from the concentrate with demineralised water. They also boil off in the same range as CMC.

All commonly available glues evaporate well below the “sticky” range of glass. You cannot rely on them to hold the glass in place until the glass tacks together with the heat.

Quickly fired glue - wet or dry - boils. Sometimes with enough force to move the glass significant distances. So, slow down the initial ramp rate.

The general observation is that if the glass will not stay in place without glue, it will move during the firing.

Glue is only useful to stabilise pieces in moving the whole assembly to the kiln. Where possible, build the piece in the kiln without glue at all.

Best of all, use no glue.

Causes of Large bubbles

 Let’s think about moisture and large bubbles from under the glass. It is not the water, but the gasses created by the decomposition of materials that can cause the bubbles. There are other causes of large bubbles too. The most common causes are discussed here.

The usual explanations are:

• ·        Uneven shelf
• ·        Heat resistant particles under the glass
• ·        Uneven heating
• ·        Glues
• ·        Organic material
• ·        Moisture
• ·        Amount of gas

 

image credit: Warm Glass

Uneven shelf

Shallow depressions in shelves can cause large bubbles. Occasionally, the shelf can be damaged in various ways causing scratches or dings in the shelf. Air can be trapped in these depressions. And it does not take much volume of trapped to be a problem. The heat of kilnforming causes the air to expand. As the glass becomes less viscous with increased temperature, the pressure from the expanding air forces the glass upwards. The amount of air and the amount of heat work combine to create bubbles from simple uprisings to large thin walled or even burst bubbles.

There are some things that can be done to detect and avoid bubbles from forming. It is possible to screed powdered kiln wash over kiln washed shelf. This gives pathways for the air to escape. It does leave a more marked bottom surface than kiln wash.

Using 1mm or 2mm fibre paper allows air from under glass. You can maintain a relatively smooth surface with Papyros or Thinfire over the fibre. Even Thinfire or Papyros on its own will allow air from under the glass.

Checking for depressions can be done by spreading kiln wash powder over shelf and drawing a straight edge over the shelf. Depressions will be shown by the presence of the powder. It can also be done with powdered glass frit.

Particles under glass

Any particle resistant to kilnforming temperatures holds the glass up while it is forming so creating an air space. It is important to ensure the shelf is clean as well as flat. Small pieces of grit or dirt that are resistant to high temperatures will hold the glass up from the shelf enough to create a bubble – small or large depending on the temperature. Vacuuming the shelf before adding anything to the surface before each firing is important to bubble free results.

Uneven heating

This is sometimes cited as a cause of bubbles. If so, the heat would need to be very localised. This is possible if the glass is very near elements. In general, the temperature is equalised at a distance equal to the width of the elements.

Glues

A wide variety of glues are used in kilnforming. Those available to enthusiasts all burn away leaving gasses between layers. These gasses - if trapped - can thin the glass below as well as above the glue’s position. This will give the impression that the bubble has come from between the shelf and the glass. Most often the bubble forms between the glass layers, pushing a bubble only into or through the top layer. The solution is to avoid using glue or minimise it and place it only at the edges.

Organic material

Organic materials can be a problem. When you are using a large or thick fibre paper sheet under a piece of glass, occasionally the gasses from burning out of the binder can be great enough to create a bubble. Although normally, this only leaves a grey to black mark on the underside of the glass. Vermiculite boards need to be fired before use, as they contain significant amounts of binder.

Inclusion of organic materials such as leaves, twigs, or bones, leads to bubbles. Very long soaks below the softening point of the glass are required to allow the organic material to burn out of the objects.  The time required increases from an hour for leaves to 24 for bones.

Moisture

Moisture is very often cited as the source of bubbles. It is possible that the steam from water may be trapped in shelf depressions, or the areas held up from the shelf. And anytime there are no precautions to allow the air from under the glass, or between sheets bubble formation can be promoted. If adequate precautions are taken (flat shelf, clean shelf, bubble squeeze) the moisture will evaporate before the glass is hot enough to form a seal around the edges and trap any steam. It is another good reason for moderate ramp rates at the beginning of a firing.

Amount of gasses

Of course, if there is a lot of moisture there can be problems. Simply applying kiln wash in four coats does not leave enough water in the shelf to be a problem.

If you have washed the kiln wash off a mullite shelf, there will be a lot of water in it even after it feels dry. Then it does need to be kiln dried before use. To avoid breaking the shelf you need to fire slowly to 99°C/210°F and soak there for a couple of hours with the vents open or lid propped up a little to allow the moisture out of the kiln.

 

 

Hot-Melt Adhesive

Some people have begun using glue guns to stabilise their glass before transporting to the kiln.  These use glue sticks which are a hot melt adhesive.

Hot melt adhesive, or hot glue, is a form of thermoplastic.  It is commonly sold in solid cylindrical sticks of various diameters designed to be applied using a hot glue gun. The gun uses a heating element to melt the plastic glue. The glue is tacky when hot, and solidifies in a few seconds to a minute. The glue squeezed out of the heated nozzle is initially hot enough to burn and even blister skin.

The glue sticks are available in a variety of melt temperatures.  The standard and most commonly available glue sticks are white to cream in colour and the guns have an orange applicator.  The hot glue is delivered from non-adjustable guns at about 195°C.  This is hot enough to burn skin and the possibility of heat shocking the glass should be considered.

3M make a low temperature variety of hot melt adhesive which needs low temperature glue guns – the 3M version is blue, and the sticks contain LT as the suffix to the part number.  This is applied at 129°C.  This is still hot enough to burn skin, but possibly with less risk of thermal shock to the glass.

The risks of breaking the glass from the heat of the glue is one of the risks.   The greater risk is of the effects of the thermo plastic on the surface of the glass.  The glue is a plastic. All of us who have left a plastic item in the kiln can witness to the black smoke created.  So, it won’t do your kiln much good, and will require firing empty to burn out all of the plastic residue. 

It also will not do you glass much good.  The thermo plastic melts and will vaporise at some (unknown) temperature.  But it will leave a residue for the process of devitrification to develop.

My recommendation is to avoid the use of hot melt adhesives for anything going into the kiln.  It is most likely to cause difficulties with the kiln and the glass.

Placing of glues

The placing of glues to hold the glass pieces temporarily is important.  Often unsightly black marks appear due to inappropriately placed glues.  Bubbles can form between layers  and even appear to come from underneath the glass for the same reason.  Placing is often more important than the amount of glue used.  Still, the amount used should be the minimum to hold the glass from moving from bench to kiln.

Place glues at edges of the pieces to be secured during movement.  This allows the burn-off of the glue to evaporate without being trapped under the glass.  If you use very runny or diluted glues, the capillary action will draw the required amount of glue under the glass piece to form a secure adhesion.

Glues burn off and leave the glass pieces unsecured long before the glass becomes tacky enough to stick together.  This means that if your stack of glass will not stay in place without glue as you build it, the glass will collapse or move in the kiln.  Glues are only suitable to stabilise the glass pieces while moving to the kiln.

Two recommended glues that burn off cleanly are the Bullseye Glasstac (more fluid) and the Glasstac gel (more viscous)

Glue boiling

People often find that their glued pieces shift in the firing.  Sometimes dramatically. This can be from placement or boiling of the glue.

Almost all commonly available glues evaporate well below the “sticky” range of glass. 

The boiling points of some of the popular glues:

PVA (also known as: wood glue, white glue, carpenter's glue, school glue, Elmer's glue in the US, or PVA glue)  

Boiling point: 112°C (234°F)

Super glue (and other cyanoacrylate glues) 

boiling point 54-56°C (129-133°F)

Lacquer (hair spray)

Boiling point: 185 to 189°C (365 to 372°F)

CMC  (carboxymethyl cellulose includes wallpaper paste, vitragel and most fusing glues)

boiling point: 260–270°C (500–518°F)  

melts at 274°C 

Aloe vera gel  

ignition point: ca. 232°C therefore, its boiling point is lower.

This shows the popular glues used in kilnforming are not effective above 300°C and many with much lower boiling points.  This means that glues only hold glass in place when cold. Glues may be useful in getting items with many pieces into the kiln, but they will not hold them in place until the glass becomes sticky.  The glass, in general, needs to be at or above the slumping temperature to begin to stick together.

If glue doesn’t work, what can I do?

Other means than glues are required to support the moveable items until the glass become sticky at around 620°C (about 700°C for float glass).

If placing frit supports is not possible without showing, such as in a tack fuse, you can use mechanical means. Two of these are grinding flat spots on rolling pieces; and placing supports under the balanced items. Other support and damming methods will depend on the nature of the project.  In general, if the pieces will not stay in place without glue before placing in the kiln, the pieces will move in the kiln after the glue evaporates.

This evaporation can be so fast as to be called boiling.  Glue boils off in the kiln whether dry before firing or not. Sometimes there is enough glue or rapid enough heating to cause displacement of the glass by the force of the boiling. Just as in boiling water, the evaporation can be explosive.  The force of the built-up pressure of glue trapped under glass can move small pieces relatively large distances.

How do I avoid boiling the glue?

• Use as little glue as possible.
• Use it at the edges of the pieces.
• Do not place it in the middle of large pieces.
• When you do use glue, advance slowly to at least 300°C allow the glue to evaporate, rather than boil.  I’d suggest a rate of 50°C per hour would be slow enough to avoid the boiling of sparingly applied glue.

Best of all, use no glue.

Quickly fired glue - wet or dry - boils.  Sometimes with enough force to move the glass significant distances.  Avoid gluing as much as possible and use sparingly when needed.

Glueing Glass Pieces

The best solution is to avoid the use of glue completely. If you cannot, use as little as possible and make sure it burns out cleanly.

The glues to which kiln workers have normal access, do not survive to tack fusing temperatures. Therefore they can only be considered as a means to get the glass assembly to the kiln. The glue will not hold the pieces in place until the glass begins to stick, so the pieces must have a stable placement. If not, the pieces will slip, roll and move once the glue has burned out.

The second requirement of glues is that they burn out without leaving a residue.

Glues that have been used with little or no residue include:

Powdered CMC that can be disolved in warm water

-CMC (carbylmethylcellulose). It is a cellulose based binder used in a wide variety of industries, including food. For our purposes, it is also used in the ceramics industry and is often called glaze binder. It is a main constituent of "glas tac" from Bullseye. This can be made up into a viscous solution to catch and hold frits and other sprinkled elements in place.

- PVA (Polyvinyl Acetate) is water-based glue. It is sometimes known as school glue. It can be diluted to about 10parts water to 1 part PVA. This is sufficient to hold the glass pieces together with only a drop for each piece of glass. It does not work so well for small sprinkled elements.

One of many brands of  Ethyl Cyanoacrylate
 glue

- Super glue burns off with no concerns about cyanide. It should be used sparingly and also works best for pieces of glass.

One of many hair laquers in pump spray bottles

- Hair lacquer is normally applied as drops at the edges of the assembled pieces and so can be used to hold pieces of glass as well as sprinkled elements.

In all uses of glue the principles to remember are:
- Use the minimum to hold pieces together while getting the work into the kiln.
- Put the glue at the edges of the glass or where its combustion gasses can escape easily.
- And in all cases, you need to test to see if a residue is left on the glass at full fuse when using a new glue.

An alternative to glue is frit as described here.

Foiling Space

There are a lot of views on what amount of space is required between copper foiled glass pieces.  Some say the pieces should be tight, others that a consistent space is needed, and some who say that variable spaces are fine.

It is necessary to consider what holds a foiled panel together.

Adhesive

The foil is supplied with an impact adhesive which helps keep the foil attached to the glass before soldering.  However, the heat of soldering deteriorates the adhesion of the glue.  If you must take a foiled piece apart you will find that the adhesive is sticky rather than firm. Also, the adhesive will continue to degrade during the life of the object.

Solder

The solder bead is significant in creating the matrix required to hold the panel in one piece.  The bead on each side holds the glass in place and resists deformation away from a single plane. This resistance is significantly reduced if there is not a fin of solder connecting the two beads.  The beads and the fin of solder form an “I” beam which together resists movement of the glass.

Strength

To form that “I” beam there does need to be space between the foiled pieces. It does not need to be wide, but it does need to be enough to wiggle the pieces.  This will allow the solder to flow from one bead to the one on the other side, forming a strong “I” beam.

In vertical panels, the glass is the strong element.  The solder lines serve to hold the matrix together.  Where people indicate the strong border will keep the whole panel from falling apart, they are correct in part. But, if there is not a sufficient “I” beam between each piece, the whole panel is subject bowing, either from wind pressure, vibration or mechanical pressure from handling.  Therefore, you cannot rely on the border to make your panel strong and long lasting.

Dissent

Some take the view that there will be enough unintentional spaces created between pieces to allow the fin form between beads intermittently.  But the gaps in the “I” beam due to tight fiting pieces will make it much weaker than a continuous bridge between beads.  The existence of gaps puts greater pressure on the solder that does bridge between beads.

An example was provided for me in a lamp brought in by client which spontaneously fell apart one evening.  (Not made by me, I add). The upper band of glass remained attached to the vase cap, but separated from the rest of the shade.  Fortunately, it fell straight down and only a little of the bottom edge was broken.  Investigation showed there was very little solder between pieces, although there was a good bead on each side of the lamp.  The lamp pieces separated, in different places, at the foil-glass interface and elsewhere at the foil to foil interface.  This indicates there was little or no solder where the foil remained on the glass, as the adhesive is much weaker than even a thin fin of solder running between the inner and outer beads. This case is an example of the need for a fin of solder to be formed between the beads on either side to provide a strong, long lasting object.

Heat Cracks

There is sometimes a fear expressed that tight fitting of foiled pieces can lead to heat fractures when soldering due to expansion.  Yes, when soldering pieces with a lot of variation in width, you do need to move reasonably quickly. Come back later to improve a bead if you need, to avoid overheating the glass.  Even the thin copper foil can transmit heat along its length, which reduces direct heat transfer to the glass.  Mostly, breaks occur from dwelling too long in one place with the soldering iron. It may be better to tin the foil all around the suspect piece just before running the bead.  This will warm the glass around the edges in preparation for the greater heat of laying down the bead.

The main point is that the solder needs to connect the beads on either side of the glass to provide a stable, strong and long-lasting piece.

Super Glue - Kiln Forming Myths 29

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 Safety

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

Alternative to Glue

Frit

Yes, clear fine frit can be a risk free alternative to glue.  Glue is to keep things in place while moving to the kiln.  Fine to medium grit can do that too.

Glass is pretty heavy and if you move the piece carefully the frit will not move and its weight will keep the other glass pieces in position.  It is better, of course, if you can build in the kiln.  Then you add the frit at the last moment to keep everything in place during the firing.  At rounded tack fuse the clear glass frit will become part of the surface. 

This method will not work for everything.  If you are using laminating or only softened edges for your tack fusing, the glass frit will remain granular.  If you have to tip or manipulate your shelf into your kiln, this will not work either.

This note indicates the use of frit to stablise stringers and rods.

Using frit to stabilise your pieces is yet another way of reducing the amount of glue usage in your work and so reduce the risk of bubbles and marks, even though the practice is not always applicable.

Stabilising Stringers

Stringers and rods never seem to stay where you put them.

• Glue them and they move after the glue has burned away.  
• Grinding a flat side to them seems a lot of work.  
• Easier, is to put them in the kiln and take them to a tack fuse to give a flat spot. But that takes a lot of kiln time.
• For stringers you can put a kink or curve in it by heating over a candle.  Rods require more heat than that. Of course, this is of no use for straight lines, and takes additional time.

A simple method which can be used with a tiny amount of glue, or not, is to add clear fine frit around the stringers and rods. This is enough to keep them from moving once the glue is gone due to the heat.

Assembled panel by Kathleen Watson with the stringers surrounded with fine clear frit which can be seen as white

The frit should be put on the assembled panel once it has been moved to and placed in the kiln.  Any movement will disturb the frit and defeat the purpose of keeping the stringer or rod in place.

The fired result

This was fused to a rounded tack fuse and no signs of the clear supporting frit is visible.

This is a quick simple method to stabilise rod, stringer and other small items that may shift in the firing.

Large Bubbles

cambridgecreativenetwork.co.uk

Some times you want large bubbles, but when you don't, you need to know about the causes of, and ways to prevent, bubbles.

Causes and prevention of most large bubbles relate to volume control, layup, rate of advance and top temperature.

Volume control. We all know that glass tends toward being 6-7mm thick at full fuse temperatures. Any less volume and the glass thickens at the edges, so trapping air under the glass which will push up and through given enough time and temperature.

Layup. The lack of volume control is compounded by layups which do not allow the air to escape from under the edges of the piece.

Rate of advance. These two problems are compounded by asap, or even just rapid, increases in temperature. The glass softens quickly and the air finds it easier to push the glass up than to escape from under the edges. Slowing down is part of the answer.

Top temperature. A high top temperature softens the glass to the extent that any lack in volume control, layups that have hollows or traps for air, and rapid increases in temperature all allow the expanding air (and there will always be some) underneath the glass to push up and often through the glass.

These factors reinforce the Low and Slow mantra.

Other factors can promote bubbles, although the ones above are the most common. Debris between the glass and the shelf, or between glass layers can cause bubbles, given the right conditions. Small shallow indentations in the shelf can be the source of bubbles from underneath the glass. This can be identified by observing where the bubbles occur in relation to the shelf.

There are some things that can be done to reduce the likelihood of bubbles:

Internal bubbles

Avoidance

Heating

Rapid firing

Damaged shelves

Supports

Flip and Fire

Glue

Flattening stringer

Placing stringer is often difficult. Not simply to put it into place, but to keep it there. People tend to hold the pieces with glue. However, the glue burns off before the stringer is anywhere near even tack fusing temperature. This allows the stringer to roll. Also an excess of glue will boil off during the heating and so move the stringer even more than gravity will. Two methods are effective in reducing the ability of the stringer to roll, by flattening one side.

Grinding

One method used by Bob Letherbarrow is to hold a stringer that is much longer than needed against the glass grinder bit. Use your thumb to hold the stringer against the bit. Slowly pull the stringer between the bit and your thumb or finger, using light pressure, to hold the stringer against the spinning grinder bit. This will slightly flatten one side of the stringer.

Firing

Another method is to place the stringers on a prepared kiln shelf, making sure they do not touch. Take the temperature quickly up to a tack fuse, soak for a few minutes and turn off. This will take only an hour or so and enables you to prepare a number of stringers with a minimum of effort.

In both cases, cut the stringer to the length needed and place on the glass with the flat side against the glass. Glue it very lightly to hold it in place while moving the piece to the kiln if it is absolutely necessary. When the glue burns off the stringer should not roll around. It is best, of course and if at all possible to place the stringers in the kiln, so no glue is needed. 

Super Glue Safety

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 be complete before firing the kiln.

See this tip for the use of super glue in kiln forming.