Grinder Bit Height

If your grinder bit is too low or too high the diamond surface will not grind the whole of the glass edge. This can lead to chipping of the surface of the glass at the edges.

Example of top of bit almost too low for the glass

A good practice is to start with the bit as high as possible to allow for differing thicknesses of glass. As high as possible is with the bottom of the diamonds just below the platform of the grinder. This will ensure that you can deal with varying thicknesses of glass without immediate adjustment. You can then lower the bit as it wears.

Example of nicely adjusted bit

Of course, you need to ensure there is adequate water reaching the grinding bit to avoid overheating the glass, and to keep the dust from grinding from getting into the air.

Mobile Glass Storage

Sometimes people consider placing their glass storage onto wheels.  It is better to avoid wheels on glass storage for several reasons.

You would need heavy duty wheels to cope with the weight. Glass is 2.5 times as heavy as water, so it does not take much volume to make a really heavy glass case.

Example of mobile glass storage

You do not need to move all your glass at once - a piece at at time is all that is needed. It will be safer, and in the end easier, to build your work bench nearer the glass.

There are risks breakage while moving. The heavy glass store will vibrate the glass within the storage, and any snags or obstructions while moving the glass will increase the risk of breakage.

The structure can become too heavy to move and so defeat the original intention.

Antiquing Sandblasted Glass

Sometimes a sandblasted area appears too white when finished. One method that can be used to tone down the whiteness is to use low temperature glass stainers' enamel.

The low temperature enamels cure at temperatures between 530C and 580C depending on the type and manufacturer. At this temperature the glass is unlikely to change its shape. The jewellers and ceramics enamels fire at higher temperatures and are not suitable.

Rub the dry powder into the sandblasted area with a cloth or your fingers. The advantage of using the powder dry is that it will not stick to the smooth areas, although you may need to brush it out of any depressions in fused glass.

Fire the glass to the minimum temperature for the enamel, but for S96 or Bullseye try to stay below 540C. This temperature will fix the paint to the glass, but not change the shape of the sandblasting. Float glass will not change if you go to 580C. If you go to higher temperatures, you will go toward a satin effect and finally a smooth surface.

This technique has the advantage of being able to introduce a subtle colour tone to the sandblasted area. This enables you to match older glass that may have a slight colour cast from the glass or materials it has become encrusted with, such as nicotine.

This method requires testing to get the right levels of colour, and the temperature to balance the fixing of the enamel without changing the sandblasted surface beyond your choice. So you need to prepare several samples noting the amounts of enamel and temperatures used.

This has been successful for me when replacing broken sandblasted door panels that need to match the side lights. It removes the excessive whiteness of the new panel and can blend to match the colour of the originals.

Assembly of Circles and Irregular Shapes.

Leading

Circles and ovals as well as irregular shapes need significant perimeter support as leading often involves sideways pressures to fit the lead to the pieces of glass. Thus there are two main methods of support .

You can cut supporting pieces of glass to place around the perimeter. These need to be cut to the outside of the perimeter cut line. These supports must be in at least two or more pieces to enable the came to be put in place progressively. You then assemble the perimeter lead into it and continue to lead up as normal. The perimeter support can also be made from thin plywood or similar materials. This can be useful if the shape is to be repeated.

A simple means of supporting irregular shapes while leading is to place a number of nails around the inside edge of the cut line. There need to be enough to support each piece of glass with at least two nails. So you may need to add more nails to the initial set up. Build the panel without the perimeter leads. When the interior is assembled, put the perimeter came around the panel. Ensure the fully leaded panel fits within the dimensions of the opening. Then solder as normal.

Copper foil

The above methods can be used, but are often a bit heavy duty for copper foil processes. Instead of glass, timber or nails you can use more easily cut materials. Such things as stiff double walled cardboard, foam board etc., are suitable for light duty. You can cut the complete shape from these materials, but only good if no pressure is used in fitting the pieces.

If you are likely to repeat the shape and size, you can use plywood or similar materials. Build inside the shape and remove it when the whole is soldered on the first side.

Disguising Joints in Fusing

You can use powder or fine frit to conceal the joints in fusing. This is most easily done before the first firing.

Fine frit can be made from the off cuts from your prepared glass, or you can buy powder of the correct colour. Where two colours meet use the darker or denser colour of frit or powder over the joint. Push the frit into place with a brush or stick to form a regular edge. You should heap the frit over the joint to allow for the reduction in volume when fused. This will not work as well on tack fusing as it does on full fused projects.

Example of frit "painting", the principal of which can be applied to glass pieces

An example of how frit can be brushed around glass pieces

Placement of Pieces for Firing

Placing pieces in the kiln, especially in oval and side fired kilns, is not about filling the kiln completely. Kilns have hot and cold spots, and the arrangement of the elements can have an effect too.

The first thing to determine with a new kiln - and immediately after any alterations to the kiln - is where the hot and cool areas of the kiln are. There is an extensive guide to this on the Bullseye site. In short, the method is to place strips of glass on short kiln furniture all around the kiln at the level(s) you will be firing. These strips should be of equal size and the kiln furniture the same distance apart. Take the temperature slowly up to slumping temperature. Observe when the visible glass pieces begin to slump. Let that continue until they are about half way down. Then proceed to the anneal. When cool you can open the kiln and see the areas where the glass has slumped most – the hotter areas – and where it has slumped least – the cooler areas. This will give you information on areas to avoid if you want an even finish all around the edges.

If your kiln is side fired, you need to consider the shelf placement in relation to the elements. The best arrangement is to have one element below the shelf and the shelf between elements so the radiant heat is not directly onto the edge of the shelf as that may lead to breaks.

Put glass on the shelf as centrally as possible. If the glass must be near the elements, baffle the glass from the direct radiant heat from the side elements.

Glues in Kiln Forming

Glues have two major uses in fusing. One is to stick things together after being fused (cold fusing). The other is to hold things together before fusing.

Holding things together while preparing the piece to be transferred to the kiln is a major use of low tack adhesives and glues. All of these burn off a lot lower than the temperature at which the glass begins to stick together. So, if you are gluing overhanging pieces, for example, they can move after the glue has burned off.  If you are assembling pieces that will not stay in place while you are putting it together, glue will not help get the final result you want.  If you are gluing to keep things stable while you move it to the kiln, you may find everything is ok.

However, glue tends to boil off if the temperature is raised too fast. During this process, the effect of the boiling will move the glass pieces that are most unstable. This also occurs if you use too much glue. You should only use as much as will stick the pieces together. Also too much glue leads to black spots and sometimes bubbles between the layers of glass.

The adhesives commonly used are the Bullseye product “Glastac”, Elmer’s glue, diluted PVA - or school - glue. All of these take varying times to dry and hold the glass pieces in place. So, a popular alternative is hair spray. This is a lacquer which dries almost instantly. It provides a thin film of adhesive and burns off in the kiln with no residue. You should use the varieties with no additives.

Glue most often leads to problems or unexpected results, so several ways have been used to achieve the desired results.

One way to deal with unstable components on small pieces is to make a large piece with a repetition of the design and cut it up after fusing in to the sizes you want.  Clean the pieces very well, and then fire them again to at least fire polish to remove any cutting or grinding marks.

An alternative to using glue, especially at the edges where the pieces are likely to move, is to use dams. My practice is to make the dams slightly taller than the unfired piece and line with fibre paper. I put 3 mm fibre paper against the dam, and thinfire against the glass. Both of these should be 3 mm narrower than the final height of the fused piece will be. This is to allow the glass to make a rounded edge as it will not be able to stick to the fibre as it sinks down to its final height.

Bullseye hot dams as an example of damming

Another alternative to using glue is to fire the piece upside down, so that the pieces do not have to be supported. This does require some planning and forethought. You can draw the design in reverse on thinfire, using different coloured pencils for the various layers to help in building the piece up in reverse. You then cap the assembled pieces with the piece that will become the bottom. Take the whole to a tack fuse. Then clean very well to remove any residues from the shelf. It is possible to sandblast and then clean to make sure there are no residues left. Of course this is not possible if you are using dichroic or iridised glass. Also note that iridised surfaces and thinfire do not get on well – there is extreme pitting in the iridised surface. 

Example of pieces glued and ready for the flip

 Once the piece is cleaned, fire again to get the desired surface texture.

Cleaning a piece after first firing

Bones as Inclusions in Glass

The major components of bones are calcium and organic materials making up the marrow. If the bones are not old and weathered a very bad smell will be produced. The organic material will cause bubbles. Finally, it takes a long time to burn out the marrow, so it is best to use bones that have weathered for a number of years.

Calcium “erodes” during firing, so fine and thin bones will leave a shadow of ash (or a big bubble if there is not a long bubble squeeze. The bone has to be encased or trapped by the glass as it will not stick permanently to the glass on its own.

It can make dramatic shapes if the bones are arranged in novel ways to represent other things. The whole of the bone does not need to be encased, as the thicker parts will be strong enough to support themselves.

Hanging Sun Catchers

Unless you are using some manufactured system or a frame, the most frequent way to provide hanging points is to create a loop from copper wire.

Hangers should originate in a solder bead that goes some way into the piece. The loop's tail should lie a significant distance into the solder line to ensure it does not pull the piece apart. If this is to remain invisible, some planning will be required to allow the small extra space between the foiled glass.

The loops for hanging a piece of any size should not be soldered to the perimeter foil without reference to the solder bead lines, as the adhesive and foil are insufficient to hold the weight of the piece without tearing.

Here the hanging loops could have been moved just a little to engage with the solder joints at the left ear and at the tail to make stronger hanging points

Here the hanging points are at the solder joints giving strong hanging points

Reinforcement of free hanging or projecting elements can be done by placing wire around the piece with a significant excess going along the perimeter in both directions. The supporting wire can go into the solder line, if it is a continuation of an edge of the free hanging piece.

In this case a twisted copper wire around the perimeter gives strong hanging points

The strongest method is to wrap the wire around the whole perimeter of the piece. Choose easily bent copper wire. This will be pretty fine, but when soldered, will be strong enough support the whole piece.

The hanger can be made by leaving a loop of wire free. This way you can hang from any convenient place on the perimeter. This loop can be made by a single 180 degree twist in the wire, or by bending a loop into the perimeter wire. In all cases you will need to tin the wire to blend it with the rest of the piece.

This perimeter wire can be simply butted at the start/finish of the wire. It could be overlapped, but this is unnecessary on any piece where this method is adequate for support. The start can be at the top or bottom, although I prefer the top, so the wire is continuous from loop to loop. The reason for continuing beyond the loops is to provide support to all the edges of the sun catcher.

This single point hanger is at the strong point of the piece

The left hanger is strong, but the right is weaker than if it had been attached to the right of the body

This piece needs wire around the piece, especially to stabilise the tail and ears

Cleaning Magnets

When making frit in steel containers the metal fragments need to be removed using magnets. It can be very difficult to get the fragments off the magnets.

A solution has been suggested. Put the magnet into a small plastic bag before use. After cleaning all the metal from the frit, take the bag to the bin and remove it from the bag. The metal fragments will drop off into the waste bin, leaving a clean magnet.

Single Layer Firing

Preparing a Single Layer for Further Kiln Work

There can be circumstances where you do want to fire a single layer in building up your project. This is more often difficult on rectangular than round pieces.

Some of the considerations are:

Temperature

Heat work

sizing

Cleaning after firing

Firing a 3 mm piece to anything over a laminated tack fuse normally leads to the edges drawing in creating a “dog bone” effect and often leading to bubbles in the interior at higher fusing temperatures. So one approach is to fire at low temperatures and accept relatively sharp edges on the piece.

Diagram of the full fused results of different thicknesses 

However the concept of heat work can help in this situation. Glass reacts to the accumulation of heat, so that slow advances or long soaks can achieve the desired results at a lower temperature without – in this case – getting the “dog bone” effect. This does require a bit of experimentation. Keep good records of all the stages of experimentation as the effects achieved with various combinations of temperature and time will come in useful later.

It is possible that using the concept of heat work will not be sufficient to achieve the desired results. Then you need to consider placing your design in the centre of a larger piece. Fire this to the lowest possible temperature to achieve your results and then cut the fired piece to size. You will need to fire polish or cold work the edges to get a suitable finish on the edges.

The central white piece shows the results of single layer firing that could be altered by the above technique

If you are going to re-fire any of these single-layer pieces, you need to clean them very well. Any dust or other contamination will be incorporated into the final piece. This is especially true if you are combining a flip and fire technique with this single-layer firing.

Slump Point Test

A slump point test is useful when you wish to determine the approximate annealing point of an unknown glass. The methodology follows:

Prepare a strip of the glass 305mm x 25mm. Suspend this strip above the shelf on 25mm pieces of kiln furniture. Leave a 275mm span between the kiln furniture. A piece of kiln furniture also needs to be placed on top of the glass to keep it in place.

Example of an extreme case of testing for slump point

Fire at 200C per hour to ca. 550C, then fire at 50C/hour to about 700C. Observe frequently from 600C. Record the temperature when the middle of span touches the shelf.  This is also the slumping temperature of the glass when fired this way. 

Subtract 40C from the “touch down” temperature for the approximate annealing point temperature.

Ceramic vs. Glass Kilns

The purposes of these two types of kiln differ, so insulation properties differ too. Ceramic kilns have high density brick insulation to retain the heat and slowly cool the contents from the top temperature to avoid breakage. Glass kilns have light weight insulation – whether brick or fibre - to cool quickly from the top temperature to avoid devitrification.

Considerations

Controllers are necessary for controlled soaks and cooling on glass kilns. Much simpler controls are sufficient for ceramics firings. So a ceramics kiln needs to have a controller added. This is a significant cost. If buying a ceramics kiln new for glass work, ensure it has a controller that can be used for glass.

A bathtub or coffin type kiln with controller

Heat distribution is different in the two. Glass kilns are shallow to get even heat distribution to the surface of the glass. Ceramic kilns have elements around the sides and frequently in the top, but may not have any in the door, if it is not top loading. This means the heat distribution in a ceramic kiln is not as even as in a glass kiln, which is not a problem for ceramics as so much heat is retained at the target temperature, it equalises as the kiln cools.

Ceramic kilns with elements on sides rather than top

Loading

Ceramic kilns up to 450 mm deep tend to be top loading, the ones with greater depth tend to have doors. Glass kilns are shallower and tend to have top – just the lid opens - , clamshell – the lid is the whole chamber which opens giving direct access to the floor of the kiln - or bell type – where the lid also forming the chamber is lifted from the base of the kiln and often the base is on wheels so another base of prepared work can be wheeled into place for firing before the kiln has completely cooled.

Large top hat kiln showing direct access to the kiln floor

Baffles are required in ceramic kilns because the heat is greater nearer the elements on the initial advance in temperature. These baffles avoid premature sealing of the edges of pieces causing large bubbles.

Firing on multiple levels is possible in ceramic once you have built up the experience.

Schedules have to take into account the greater mass of insulation in ceramic kilns.

Kiln with fibre insulation all around

Annealing and cooling tends to require different strategies to encourage the ceramics kiln to cool fast enough in the devitrification range, but can have the power turned off earlier after the annealing soak, because of the slower cooling.

Large front loading ceramic kiln

Ceramic kilns are ideal for casting.

Cost – ceramic kilns tend to cost less than glass ones and second hand ones have been more widely available. That may be changing now with the increasing popularity of glass fusing. 

The electricity costs are marginally higher in ceramic kilns than glass, because the mass of brick to be heated up is greater..

Space - Ceramic kilns tend to take up less floor space because they are deep or tall rather than broad.

Small top loading kiln with combination brick and fibre insulation

Removing Kiln Wash

Kiln wash can get stuck on items for a variety of reasons. 

A variety of ways to remove the kiln wash are:

Grind the kiln wash off with diamond hand pads, or small rotary tool with wet sandpaper. You can then proceed to continue to grind with successively fine grits until a polish is achieved, or you can fire polish after a thorough cleaning.

Example of scrubbing kiln wash off

You can sandblast off the kiln wash and then proceed in either of the fashions above.

You can soak small pieces in tri-sodium citrate and then if necessary scrub with a wire brush – a brass wire brush is preferable to steel one to avoid scratching the glass.

Another solution is to place small items in an ultrasonic cleaner basket with water and a little soap or proprietary cleaner. Leave for an hour or two and they should be free of the kiln wash.

A link to some methods of cleaning shelves is here.

Grinder Chipping Glass

There are a number of reasons that may cause the grinder to chip the glass surface. Some of the things to check are:

Too much pressure

It may be that you are pressing the glass into the grinder head too hard. The grinder head should do the work. Firm rather than hard pressure should be applied. If the grinder slows, it is an indication that far too much pressure is being applied.

Insufficient water supply

There may be too little water reaching the head to lubricate the diamonds and keep the glass cool. If you are getting a white paste or a powder on or near the glass, you need to increase the water supply.

Worn or damaged grinder bit/head

Inspect your bit carefully for smooth areas showing that the diamonds have been worn away. Also look for dents, and other irregularities on the surface, indicating that the bit is damaged. Any dents or smooth places on the bit cause a vibration that is similar to a tiny hammer tapping the edge of the glass.

Grit size

It is possible that you may be using too coarse a grit on the grinder bit/head. The more coarse the grit is the larger the chips will be taken off the edge surfaces. Smaller grits take smaller chips off the edges, and so are less obvious.

New bits

Examples of the range and grit differences in grinding bits

If it is a new bit that is causing the chipping, consider dressing it. New bits often need to be dressed – removing protruding diamonds, or cleaning and exposing new ones on a worn bit. To dress the bit you can grind some scrap glass, brick, or use a dressing stone to lightly grind some of the abrasive material away. This most often settles the bit and avoids chipping.

Cutting thick glass

Use the correct angle of cutter wheel for the thickness. 

Use a similar pressure to cutting 3 or 6 mm glass. It is natural to think that as the glass is thicker, you need to use more pressure. The different angle of the cutter wheel is designed to transfer the standard pressure more directly downward.

Use cut runners made for thick glass to help break the glass. Run score from both ends of the score, especially on curved scores.

Example of cut runners for thick glass

Alternatively, turn the over and use hammer and rounded screw driver to run the score (similar to tapping method for thinner glass). Place the screw driver blade directly over the score line and tap it with a hammer. This will start the run. Continue it by placing the screw driver over the score at the end of the open score and tap again to continue the run.

Air Brushing on Glass

Raphael Schnepf Workshop

Air brushing onto glass is a little different than onto other slightly absorbent surfaces. As glass cannot absorb the moisture from the material being sprayed, the medium needs to be allowed evaporate. This means that each layer of paint must be allowed to dry before the next layer is applied. If too much liquid is applied to the glass, it will bead up giving a stippled appearance to the finished result.

There are some things that can help to give an even application of the paint or enamels to the glass.

Clean the glass very well. After thorough cleaning and drying, use some of the paint to rub the glass. As the paint is a slight abrasive, it cleans off anything the other cleaning methods could not get off.

Add a drop of washing up liquid to the mixture of paint and medium (liquid). This breaks the surface tension of the medium and reduces the tendency to bead up on the glass.

Use alcohol part or all of the medium. This reduces the evaporation time. Also apply in a warm rather than cold place. You can use a hair dryer on low speed and power to assist the drying.

Apply in thin even layers, allowing the paint to dry between applications.

Open the air brush trigger before reaching the edge of the area to be painted and close it after reaching the other edge. Any overspray can be cleaned up as in any other painting.

A slightly larger opening at the nozzle is required on the air brush than for other paints, but you have to be careful to avoid opening it so large that you get the spitting of large drops of paint onto your surface.

Because you are putting very small particles into the air you need to observe various precautions. You need to have a dust mask on at all times you are air brushing. You should do this in a spray booth with extraction if possible. If not, you need a well-ventilated area and very good clean up afterwards.

Avoiding Large Bubbles

“I tried small projects and they turned out fine. I have a 12" square with an emblem in the centre and a border set in slightly from the sides. Most of the glass is only the one layer. Both firings produced huge bubbles in the areas where the glass was only one thickness.”

Scale does matter. What can be done at a small scale does not always transfer to a larger scale without alteration.

 

The first problem this project created was using only one layer as the base. Glass has a surface tension which means that it tries to become 6-7 mm thick, which is twice the thickness of a single layer. As it thickens at the edges, it traps the air under other parts of the glass, and as the glass continues to soften the expanding air bubbles come up through the thin parts of the glass.  Using two layers of glass with the design on top will ease the problem.

 

The design is the second problem. The weight of the border makes it even more difficult for the air to get out from under the glass.  Although having two layers of glass will reduce the problem, think about ways to make the border incorporated with the second layer of glass, so the weight of the glass at the perimeter is not greater than the interior.

 

The third problem is that there is not a bubble squeeze in the schedule (indicated elsewhere in the query). The soak of 10 minutes at 538ºC/1000ºF is not necessary. You do need a soak at a point between 620ºC/1148ºF and 677ºC/1250ºF - this is the bubble squeeze temperature range. It is also the slump temperature, so you can determine what the bubble squeeze should be for your glass by what the upper slump temperature is.

 

The bubble squeeze can be accomplished by a half hour soak at the slump temperature, or by a slow rise from 50C below the slump temperature – taking an hour or so, depending on the size of the piece.

 

A fourth problem is the that the separator is kiln wash, and the edges of the glass conformed to the kiln wash, resisting the movement of air from under the glass.

 

You may need to change to fibre paper for single layer pieces, as that allows more air out. Shelf paper may be enough, but you can also put it over 0.5 mm fibre paper for greater air release. Alternatively, sprinkle powdered kiln wash over the fibre paper and smooth it if you don't want to use Thinfire.

 

Lastly, try to avoid the factory set schedules in your kiln's controller, as they are generally set for 6mm thick pieces.

 

Look at the glass manufacturer's website. Bullseye, Spectrum, Uroboros, and Wissmach give basic firing schedules that work with minimal adjustment. I don't understand why kin manufacturers don't simply refer to the manufacturers’ sites to give their customers good advice, instead of the pre-programmed stuff.

Orientation of Cutter Heads

In addition to the alignment of the cutter, you need to be sure you are moving the cutter forward in the way it was designed. If you look at the cutter from the side you will see two things. The most obvious one is that the angles of the cutaway on the head are shallower at the front and steeper at the back. In addition if you look carefully, the axel for the wheel is slightly forward of the centre line of the whole cutter.

Cutters aligned to score to the left

So it does not matter where the fixing screw on the head is. It may be at the front or at the back. What matters is the cutaway at the back which allows the cutter to be used with a shallower angle, than if reversed. This is most obvious on wide cutter heads.

Cutters arranged to score to the right

Repair of a Plastic Barrel Cutter

Generally, there are two parts that can break or be damaged – the wheel and the barrel.

Wheel

If the wheel is damaged or worn, you can replace the head. When considering that, look at the cost of the head and consider whether the small cost difference indicates you should buy a new cutter instead.

The most common damage is a flat spot on the wheel. You can check for this, immediately after dropping the cutter, by lightly moving the cutter across a smooth piece of glass. If you hear a regular ticking sound, the wheel is probably “flat spotted” and will need to be replaced.

A worn wheel is more difficult to detect and is also much less likely to occur. I have been using some of my cutters for 15 years without any sign of being worn.

Plastic barrel

Sometimes the plastic barrel cracks or breaks. This will mean that the oil in the cutter will leak out. So you can consider continuing to use the cutter without oil, or by dipping the head in an oil soaked bit of cotton wool or similar material before each cut.

If the break is at the threaded end and you want to continue to use the ball at the end for tapping purposes, you can glue the barrel back together with an epoxy resin. Make sure the pieces are free from oil. Then glue and allow to cure. After curing, sand down any excess resin to make the cutter comfortable to handle.

Then for additional strength you can wrap with dental floss or extremely fine wire. Start below the glued area and go to the end of the break and back again. You could coat this wrapping with epoxy again both to secure the wrapping and to further increase the strength.

Another solution is to cut the cracked end off and re-thread the remainder. It makes the cutter a little shorter, but will continue to hold oil and give good service.

Or, you could buy another cutter.

Gas Fired Kilns

Installing a Gas Fired Kiln

There are a number of considerations about the location of a gas kiln.

Air exchange

The kiln should be placed in an area where there is good air exchange. For a number of reasons, it is usually convenient to place the kiln near an outside wall – ventilation and canister storage are the two most important.

Ventilation

There should be a low level vent to the outside to allow air to rise for the use of the combusting gas. There needs to be high level vent for the gas to escape. Ideally a hood with powered extraction would be installed.

Space

As with any kiln, you need to have sufficient space around the kiln to avoid heating any flammable materials. In the case of a gas kiln you need to be careful to avoid storing any thing that might ignite above the kiln. You can put heat resistant materials around the kiln if desired.

Location and storage of gas canisters

The safest place to put the gas canisters is outside the building. This does mean going outside to turn the valve on the gas canister on and off. However this is the safest place, should any fire start in the building, because the fire brigade can find and remove it from the fire. This placing applies to both the in use canister and any other full or empty canisters.

Detectors

Finally, even with these precautions, you should install a carbon monoxide detector. Carbon monoxide has no smell and can overcome you very quickly. Even a few minutes of exposure can leave you feeling ill for days.  

Paint and Cold Working

One of the difficult things in cold working is determining when it is time to move on to the next grit size.  You really cannot tell while the piece is wet, because the water disguises the minute scratches put into the glass by the grinding process.

After you have dried the piece, you can coat it with a white paint pen. It is not necessary to cover the piece completely in white pen.  The white marks will be taken away by the grinding to give evidence of where you have already ground the piece.

Piece prepared for the next stage of grinding

You must make sure the paint has completely dried, or it will wash off with the water used in the grinding.

I find I get best results from this "witness" by making the paint pen marks at right angles to the grinding direction.  When all traces of the paint have disappeared, you have thoroughly covered the piece with that grit size.  Being ever cautious, I tend to dry, paint and do a second pass at the same grit before going to the next finer grit.