Home Made Billets

You can make your own billets from small pot melts.  But why should anyone go to the effort? Some reasons are:

• ·        You can make your own colour. 
• ·        You can use your cullet/scrap (avoiding buying or making frit).
• ·        You don’t have to buy and break billet to size 
• ·        You can reduce the clouding caused by many microscopic bubbles surrounding the frit pieces. 
• ·        You can make a size to fit your casting mould. 
• ·        Potentially, you will reduce needling.

 Now you are convinced of the advantages, you want to know how.

Preparation

• ·        Select the glass. Avoid iridised glass and any ground edges – they will cause haze in the final casting. Wash all the glass. Place the glass in a small flowerpot.
• ·        Weigh out the amount of glass cullet needed for the mould and add about 50gms to account for the glass that will stick to the pot.  Calculating the required weight is relatively simple and this post gives the information.

Dams

• ·        Arrange dams in such a way that the resulting billet will fit into the mould without overhang.  It might be quite a tall billet. In which case cast it horizontal with the height as the length of the billet.
• ·        Line the dams with Thinfire/Papyros at least. One mm fibre paper would be better. 
• ·        The dams can be on a kiln washed shelf or on fibre paper. The bottom of the glass will be fine either way.
• ·        Place the pot above the dams.  The higher, the fewer bubbles in the billet.  And any left in the billet will be reduced by flow in the casting firing.
• ·        Multiple billets can be made of different colours, sizes, etc., at the same time.

Firing

• ·        Fire to around 900ºC/1650ºF and soak for hours.  Observation will show when the pot is empty.  Clue: There will be no string of glass from the bottom of the pot.
• ·        Anneal as for the smallest dimension.  If you are doing multiple sizes, the dimension must be taken from the biggest piece.
• ·        When cool, remove and clean the separator off the pieces thoroughly.  A 15 minute soak in a 5% citric acid solution will speed the process.

Casting

• ·        Place billet in casting mould. The first ramp rate needs to be for the smallest dimension of the billet.  This may be a slower rate than when using frit for casting.
• ·        Do a long bubble squeeze in the 650ºC to 670ºC range – up to two hours, but a minimum of one.
• ·        Fire to your normal top temperature and time.
• ·        Anneal for the largest piece.

 

More information here 

Effects of Dam Materials on Scheduling

 I once made a statement about the effects of various dam materials on scheduling. This was based on my understanding of the density of three common refractory materials used in kilnforming – ceramic shelves, vermiculite board and fibre board. I decided to test these statements.  This showed I was wrong in my assumptions.

I set up a test of the heat gain and loss of the three materials. This was done without any glass involved to eliminate the influence of the glass on the behaviour of the dams. The dam materials were laid on the kiln shelf with thermocouples between. These were connected to a data logger to record the temperatures.

Test Setup

 The thicknesses of the dams may be relevant. The vermiculite and fibre boards were 25mm thick. The ceramic dam material was 13mm thick.

The schedule used was a slightly modified one for 6mm:

• 300°C/hr to 800°C for 10 minutes
• Full to 482°C for 60 minutes
• 83°C to 427, no soak
• 150°C to 370°C, no soak
• 400°C to 100°C, end

 

The data retrieved from the data recording is shown by the following graphs.

Temperature profile of the air, ceramic, fibre, and vermiculite during the firing.

Highlights:

• The dam materials all perform similarly.
• This graph shows the dams have significant differences from the air temperature – up to 190°C – during the first ramp of 300°C/hr. (in this case).
• There is the curious fall in the dams’ temperatures during the anneal soak. This was replicated in additional tests. I do not currently know the reasons for this.
• The dams remain cooler than the air temperature until midway during the second cool when (in this kiln) the natural cooling rate takes over.
• From the second cool to the finish, the dams remain hotter than the air temperature.

 Some more information is given by looking at the temperature differentials (ΔT) between the materials and the air. This graph is to assist in investigating how significantly different the materials are.

This graph is initially confusing as positive numbers indicate the temperature of the first is cooler than the material it is compared with, and hotter when in negative numbers.

 

A= air; C=ceramic; F=fibre board; V=vermiculite

Temperature variations between air and dams

 As an assistance to relating the ΔT to the air temperature some relevant data points are given. The data points relate to the numbers running along the bottom of the graph.

 Data Point       Event

• 1            Start of anneal soak.
• 30          Start of 1^st cool (482°C)
• 45          Start of 2^nd cool (427°C)
• 65          Start of final cool (370°C)
• 89          1^st 55°C of final cool (315°C)
• 306         100°C

 

At the data points:

• At the start of anneal soak the ΔT between the dams is 16°C with the ceramic shelf temperature being 18°C hotter than the air.
• At the end of the anneal soak of an hour, the air temperature is 20°C higher, although the ΔT between the dams has reduced to 12°C.
• At the end of the 1^st cool the ΔT between the dams has reduced to 9°C and the ΔT with the air is 3°C.
• At approximately 450°C the air temperature becomes less than the dams.
• At 370°C the hottest dams are approximately 17°C hotter than the air.  The ΔT between the dams is 10°C.

 More generally:

• The air temperature tends to be between 17°C hotter and 17°C cooler than the ceramic dams during the anneal soak and cool.  The difference gradually decreases to around 8°C at about 120°C.
• Ceramic and fibre dams loose heat after the annealing soak at similar rates – having a ΔT between 4°C and 1°C, with a peak difference of 9°C at the start of the second cool. This means the heat retention characteristics of ceramic strips and fibre board are very close.
• Between the annealing soak and about 300°C the vermiculite is between 12°C and 9°C hotter than the same thickness of fibre.  Vermiculite both gains and loses heat more slowly than the ceramic or fibre dams do. This means that vermiculite is the most heat retentive of the three materials.
• Vermiculite remains hotter than ceramic from the start of the second cool. This variance is up to 9°C and decreases to 3°C by 100°C.
• Fibre board is cooler than ceramic dams until the final cool starts, when there is little variance.  At the start of the second cool there is about 15°C between the two.
• Vermiculite remains cooler than fibre dams throughout the cooling process. This ranges from about 12°C at the start of the first cool to about 3°C at 100°C.

Since we cannot see more than the air temperature on our controllers it is useful to compare air and dam temperatures. The same data points apply as the graph comparing differences between materials.

 

Ceramic-Vermiculite; Ceramic-Fibre Board; Vermiculite-Fibre Board; Ceramic-Air Temperature
This graph shows the temperature differences throughout the cooling of various materials.

• During the annealing soak, the air temperature is greater than the dam temperatures. The fibre and vermiculite boards remain at similar temperatures and the ceramic dam is the coolest.
• The three dam materials even out with the air temperature at the start of the second cool.
• Through the second and final cools, vermiculite dams remain hotter than the air temperature – between about 24°C at start of the final cool and 9°C at 100°C.
• The ceramic and fibre dams are close in temperature difference to the air from the start of the final cool. Their ΔTs are 17°C at the start of the final cool and 6°C at 100°C.

Conclusions

• Dams will have little effect during the heat up of open face dammed glass.  The slight difference will be at the interface of the glass and the dams where there will be a slight cooling effect on the glass. Therefore, a slightly longer top soak or a slightly higher top temperature may be useful.
• The continued fall in the dams’ temperature during the anneal soak indicates that this soak should be extended to ensure heat is not being drained from the edges of the glass by the dams. There is the risk of creating unequal temperatures across the glass.
• The ability of ceramic and fibre dams to absorb and dissipate heat more quickly indicates that they are better materials for dams than vermiculite board. The slightly better retention of heat at the annealing soak, indicates that ceramic is a good choice when annealing is critical.        
• These tests were fired as for 6mm/0.25” glass and so show the greatest differences. Firing for thicker glass will use longer soaks and slower cool rates. These will allow the dams to perform more closely to the glass temperature during annealing and cool.

Based on these observations, I have come to some conclusions about the effect of dams on scheduling.

• There is no significant effect caused by dams during the heat up, so scheduling of the heat up can be as for the thickness of the glass.
• The lag in temperature rise of the dams indicates a slightly longer soak at the top temperature (with a minor risk of devitrification), or a higher temperature of, say 10°C, can be used.
• The (strange) continued cooling of the dams during the annealing soak indicates that extending the soak time to that for a piece 6mm thicker than actual is advisable.
• The cool rates can continue to be as for the actual thickness, as the dam temperatures follow the air temperature with little deviation below the end of the first cool.
• Ceramic dams of 13mm/ 0.5” perform better than 25mm/1.0” vermiculite and fibre board. 
• However, in further tests of 25mm/1.0” thick ceramic dams performed similarly to the same thickness of vermiculite. So, 25mm/1.0” fibre board the best when choosing between the three materials of the same thickness. But 25mm ceramic strips are not common, nor are they needed for strength or weight.
• The performance of the three dam materials tested do not show enough difference in temperature variation to have significant affects on the annealing and cooling at times and rates appropriate to the thickness of the glass.
• It is the thermal insulation properties of the dam material, rather than the density that has the greatest influence on performance as a dam material.

 

 

Damming for Exact Shapes

 Many times, exact dimensions of the final piece are not critical.  When they are and the piece is 9mm and thicker, or has irregular amounts of glass near the edge, damming is required.

 If the dimensions are rectangular, you can use straight edged refractory materials, usually sawn up broken kiln shelves, vermiculite, or fibre board strips.  

 These need to be kiln washed and lined with fibre paper.  The dams should be lined with 3mm fibre paper that is 3mm narrower than the final height of the piece.  This allows a bullnose shape at the edge to form.

 If the shape is a circular or irregular shape the dams can be made from thick fibre board or vermiculite.  The lining of the dams is the same as for rectangular shapes.  

 The use of 3mm fibre paper means that you have to make rectangular shapes 6mm bigger in each direction to achieve the exact final dimensions.  For circular or irregular shapes, the edge will need to be only 3mm larger.  This is because the edge goes around the whole shape, rather than only one side.

 

Effects of Dams on Scheduling

 I recently made a statement about the effects of various dam materials on the scheduling.  This was based on my understanding of the density of three common refractory materials used in kilnforming – ceramic shelves, vermiculite board and fibre board.  I decided to test these statements.  I found I was wrong.

I set up a test of the heat gain and loss of the three materials.  This was done without any glass involved to eliminate the influence of the glass on the behaviour of the dams.  The dam materials were laid on the kiln shelf with thermocouples between.  These were connected to a data logger to record the temperatures.

 

The schedule used was a slightly modified one for 6mm:

300°C/hr to 800°C for 10 minutes

Full to 482°C for 60 minutes

83°C to 427, no soak

150°C to 370°C, no soak

400°C to 100°C, end

 

The data retrieved from the data recording is shown by the following graphs.

 

Highlights:

·        The dam materials all perform similarly. 

·        This graph shows the dams have significant differences from the air temperature – up to 190°C – during the first ramp of 300°C/hr. (in this case). 

·        There is the curious fall in the dams’ temperatures during the anneal soak.  This was replicated in additional tests.  I do not currently know the reasons for this.

·        The dams remain cooler than the air temperature until midway during the second cool when (in this kiln) the natural cooling rate takes over.

·        From the second cool to the finish, the dams remain hotter than the air temperature.

 

Some more information is given by looking at the temperature differentials (ΔT) between the materials and the air.  This graph is to assist in investigating how significantly different the materials are. 

This graph is initially confusing as positive numbers indicate the temperature is cooler than the material being compared and hotter with negative numbers.

 

As an assistance to relating the ΔT to the air temperature some relevant data points are given.  The data points relate to the numbers running along the bottom of the graph.

Data Point   Event

    1                Start of anneal soak.

    30              Start of 1^st cool (482°C)

    45              Start of 2^nd cool (427°C)

    65              Start of final cool (370°C)

    89              1^st 55°C of final cool (315°C)

    306             100°C

 

At the data points:

·        At the start of anneal soak the ΔT between the dams is 16°C with the ceramic shelf temperature being 18°C hotter than the air.

·        At the end of the anneal soak of an hour, the air temperature is 20°C higher, although the ΔT between the dams has reduced to 12°C.

·        At the end of the 1^st cool the ΔT between the dams has reduced to 9°C and the ΔT with the air is 3°C.

·        At approximately 450°C the air temperature becomes less than the dams. 

·        At 370°C the hottest dams are approximately 17°C hotter than the air.  The ΔT between the dams is 10°C.

 

More generally:

·        The air temperature tends to be between 17°C hotter and 17°C cooler than the ceramic dams during the anneal soak and cool.  The difference gradually decreases to around 8°C at about 120°C.

·        Ceramic and fibre dams loose heat after annealing at similar rates – generally having a ΔT between 4°C and 1°C, with a peak difference of 9°C at the start of the second cool. This means the heat retention characteristics of ceramic strips and fibre board are very close.

·        Between the annealing soak and about 300°C the vermiculite is between 12°C and 9°C hotter than the same thickness of fibre.  Vermiculite both gains and loses heat more slowly than the ceramic or fibre dams do.  This means that vermiculite is the most heat retentive of the three materials.

Conclusions

·        Dams will have little effect during the heat up of open face dammed glass.  The slight difference will be at the interface of the glass and the dams where there will be a slight cooling effect on the glass.  Therefore, a slightly longer top soak or a slightly higher top temperature may be useful.

·        The continued fall in the dams’ temperature during the anneal soak indicates that this soak should be extended to ensure heat is not being drained from the glass by the dams to give unequal temperatures across the glass with the risk of inadequate annealing.  I suggest the soak should be extended to that for glass of 6mm thicker than actual to account for this.

·        The ability of ceramic and fibre dams to absorb and dissipate heat more quickly indicates that they are better materials for dams than vermiculite board.  The slightly better retention of heat at the annealing soak, indicates that ceramic is a good choice when annealing is critical.

Scheduling Effects 

Based on these observations, I have come to some conclusions about the effect of dams on scheduling.

·        There is no significant effect caused by dams during the heat up, so scheduling of the heat up can be as for the thickness of the glass.

·        The lag in temperature rise by the dams indicates a slightly longer soak at the top temperature (with a minor risk of devitrification), or a higher temperature of, say 10°C can be used.

·        The (strange) continued cooling of the dams during the annealing soak indicates that extending the soak time to that for a piece 6mm thicker than actual is advisable.

·        The cool rates can continue to be as for the actual thickness, as the dam temperatures follow the air temperature with little deviation below the end of the first cool. 

·        Ceramic dams perform the best of the three tested materials.

 

Expansion at Edges of Tack Fused Stacks

How much will my glass expand if I put glass pieces on top of 6mm base?  

I ran some tests for both 6mm and 3mm bases. These showed that the distance from the edge is important.  The amount of glass in the stack has a big influence on expansion.  So does the tack profile and the thickness of the base.

The most expansion for any thickness and at any tack profile is when the stack is placed at the edge.  The further away from the edge, the less the expansion. There is no noticeable expansion of size when the tack stacks are placed 20mm from the edge.  In most cases there is only a little expansion at 10mm from the edge.  Although not tested, it seems that 15mm is a safe distance from the edge to avoid changing the edge.

The amount of glass in the stack being tacked to the base has an effect on the amount of expansion.  This is to be expected based on the concepts behind volume control.  Two tack layers can vary from two to three times that for a single tack layer depending on the profile of the tack.

The tack profile has an effect on the amount of expansion.  At contour there is a greater expansion than at rounded or sharp tack fuse.  This is to be expected, as there is less heat work at sharper tack profiles than at contour.

The thickness of the base has an influence on the amount of expansion too.  Thicker stacks promote greater deformation of the edge at all tack levels.  Thicker stacks need to be placed further from the edge to avoid changing the perimeter.  Thicker stacks create greater change in the edge on single layers than double layers.

The setup and results are given here.

Setup for 2 layer base and 1 and 2 layer stacks at various distances from the edge.

Contour fuse test, 6mm base
1 layer placed at edge, at 10mm from edge, at 20mm from edge, and at 30mm from edge.  2 layer stacks placed in the same way.  
 

Fired results, outlined for clarity

1 layer placed at edge – expansion of 2.5mm
1 layer placed 10mm from edge – expansion of 0mm
1 layer placed 20mm from edge – expansion of 0mm
1 layer placed 30mm from edge – expansion of 0mm

2 layers place at edge – expansion of 9mm
2 layers placed 10mm from edge – expansion of 2mm
2 layers placed 20mm from edge – expansion of 0mm
2 layers placed 30mm from edge – expansion of 0mm
 

Rounded tack test, 6mm base
1 layer placed at edge, at 10mm from edge, and at 20mm from edge.
2 layer stacks placed in the same way.
 
1 layer placed at edge – expansion of 3mm
1 layer 10mm from edge – expansion of 0mm
1 layer 20mm from edge – expansion of 0mm

2 layers place at edge – expansion of 7mm
2 layers placed 10mm from edge – expansion of 1mm
2 layers placed 20mm from edge – expansion of 0mm
 

Fired result of 6mm base with 1 and 2 tack layers, rounded tack.

 
Rounded tack test, 3mm base
1 layer placed at edge, 1 at 10mm from edge, 1 at 20mm from edge, 1 at 30mm from edge.  2 layer stacks placed as above.  
 
1 layer placed at edge – expansion of 2.5mm
1 layer 10mm from edge – expansion of 1mm
1 layer 20mm from edge – expansion of 0mm
1 layer 30mm from edge – expansion of 0mm
 
2 layers placed at edge – expansion of 3mm
2 layers 10mm from edge – expansion of 1mm
2 layers 20mm from edge – expansion of 0mm
2 layers 30mm from edge – expansion of 0mm
 

Fired result of 3mm base with 1 and 2 tack layers.

Note: the single 200mm sheet contracted to 195mm in uncovered areas.  Measurements were based on the amount of expansion from the fired dimensions. Even with the greatest expansion the piece was still 2.5mm smaller after firing than at the start.
 

Sharp tack test, 6mm base
1 layer placed at edge, 1 at 10mm from edge, 1 at 20mm from edge, 1 at 30mm from edge.  2 layer stacks placed as above.  

 
1 layer placed at edge – expansion of 1mm
1 layer 10mm from edge – expansion of 0mm
1 layer 20mm from edge – expansion of 0mm
1 layer 30mm from edge – expansion of 0mm
 
2 layers placed at edge – expansion of 2mm
2 layers 10mm from edge – expansion of 0mm
2 layers 20mm from edge – expansion of 0mm
2 layers 30mm from edge – expansion of 0mm
 

More detailed information is available in the e-book: Low Temperature Kilnforming.

Pot Melt Saucers as Dams for Melts

Preparation

Many ceramic plant pot saucers can be used as circular moulds.  Most are unglazed and will accept kiln wash easily.  Some are unglazed, but polished to such an extent they are no longer porous.  These and glazed flower pot saucers need some preparation before applying kiln wash.

Plant pot with saucer

Polished and glazed saucers require roughing to provide a key for the kiln wash solution to settle into.  This can be done with normal wood working sand papers.  You may want to wear a dust mask during this process, but not a lot of dust is created.  You could also use wet and dry sandpaper or diamond handpads with some water to reduce the dust further.

If the sanding of the surface does not allow the kiln wash to adhere to the saucer, you can heat it.  Soak it at about 125C for 15 minutes before removing it from the kiln to get the heat distributed throughout the ceramic body.  One advantage to the ceramic is that it holds the heat, because of its mass, for longer than steel.  Apply kiln wash with a brush or spray it onto the warm saucer.  As it dries, apply another layer of kiln wash.  Two or three applications should be enough to completely cover the surface.  If not, then you probably will need to heat up again before repeating the process.

Alternatives to plant pot saucers

There are alternatives to the saucer approach to getting thick circles from a pot melt.

 

Fibre paper

You can cut a circle from fibre paper and melt into that.  The advantage of fibre paper is that it requires little preparation other than cutting and fixing.  You may have only 3mm fibre paper and want a 9mm thick disc.  Simply fix the required number of layers together with the circle cut from each square.  The fixing can be as simple as sewing pins, copper wire, or high temperature wire.  Then place some kiln furniture on top of the surrounding fibre paper to keep it in place on the shelf during the melt.  This furniture can often be the supports for the melt.

Fibre board

If you find cutting multiple circles of the same size a nuisance, you can use fibre board.  Simply cut the circle from the board with a craft knife.  You will probably want to line the circle with fibre paper, as the cut edge of fibre board can be rough.  Alternatively, you can lightly sand the edge.  Wear a dust mask and do this outside, if possible, to keep the irritating fibres away from the studio. If you want a thicker melt than one layer of board can give, just add another in the same way as for fibre paper.

In both these cases, you may wish to put down a layer of 1mm fibre paper to ensure the glass does not stick to the shelf and does not require sandblasting.  

The advantage of the fibre paper or board alternative to flower pot saucers is that you do not need to kiln wash anything unless you want to. If you do not harden the fibre paper or board, it will not stick to the glass.

Vermiculite board

Another alternative is vermiculite board.  The advantage of this is that it comes in 25 and 50 mm thicknesses, so you can make the melt as thick as you like without having to add layers.  You can cut the vermiculite board with wood working tools.  Knives will not be strong enough to cut through the vermiculite board. You will need to kiln wash or line the vermiculite with fibre paper, as the board will stick to the glass without a separator.

Damless circles

Of course, if you want a circle without concern over the thickness, you can do the melt without any dams. You need to ensure that the shelf is level.  Any supports for the pot will need to be both kiln washed and far away enough that the moving glass does not touch the supports and distort the circle.  In general, one kilogramme of glass will give a 300mm circle, so your supports need to be further apart than the calculated diameter of the circle.  An undammed circle will vary from 6mm at the edge to as much as 12mm at the centre, depending on temperatures and lengths of soaks.

Damming Ovals

There are various ways of damming oval shapes in kiln forming. Some of these are outlined here.

One set of methods depends on having a soft surface such as ceramic Fibre board or vermiculite.

Photo from Clearwater Studio

You can wrap your shape with fibre paper. For this you need to cut a strip or strips 3mm narrower than the height of the piece you are wrapping. You then stick sewing pins down through the fibre paper and into the shelf of fibre board or vermiculite. This will be easiest if you use 1 to 3mm thick fibre paper, as the pins must not contact the glass – the pins will stick to the glass if they do.

You can cut a form out of ceramic fibre board and use that as a dam. You can pin this to the base fibre board or allow it to merely rest on the board. It is possible to cut arcs from fibre board and place them around in sections. In this case they will need to be pinned together so they do not move apart. Staples can form the attachments. You can make your own – larger – ones from copper wire.

You can buy stainless steel banding which needs to be lined with any separator – batt wash or fibre paper.

Bonny Doon stainless steel dams

You also can layer fibre paper up to the height required – remember 3mm less than the thickness of the piece. You then need to fasten the layers together to avoid movement between the layers.


If you are firing on ceramic kiln shelves the same materials can be used but need to be supported a little differently.

If you are wrapping the piece on mullite shelves, use some pieces of kiln furniture to block the strips up against the glass. The thicker the glass, the more weight will be pushing out against the dams and the sturdier the dams will need to be. Make sure the strips contact the shelf evenly- if you have gaps, you'll have leaks.

The disadvantage to this method is that the glass can take up the irregularities of the kiln furniture.

You can use fibre board with a void cut out to the shape required and place it on the shelf.

You can also use layers of fiber paper around the shape and pin the layers to each other. This is the same method as used on ceramic fibre board.

Again stainless steel can be used to form the dam. Remember to line the steel with fibre paper that is 3mm narrower than the height of the piece.



In all these cases of dammed forms, the edges will be of varying degrees of roughness and some cold working will be required.

Fibre Dams

Fibre dams are a good and relatively inexpensive refractory material to form dams around regular and especially irregular shapes.  You need only cut the shape you want from the fibre board, if it is not a shape with straight lines.  

You can fire without any kiln wash or hardening if it is a one-off use.  For shapes you want to keep, you can harden the fibre board. 

Once hardened with colloidal silica, you need to paint the board with a separator – kiln wash, boron nitride or similar.

There are some precautions in the use of fibre paper and board.  The main physical one is that refractory fibre is lighter than glass and so will float on top of “molten” glass – that is fusing compatible glass higher than about 800°C.

Fibre board dams can be weighted with kiln furniture on the surface of the board.  If the board is flat this can be on the surface.  If the board is vertical, weights can be placed at the corners.

In the absence of fibre board, you can use layers of fibre paper.  If you have 6mm fibre paper, you need only one layer for two-layer glass, but remember that to get a bullnosed edge to the glass without needling, the fibre paper should be 3mm less than the final height of the fired piece. Thicker glass will require more than one layer of fibre paper.  Place as many layers of fibre paper as required to be at least equal in height to the finished piece on top of one another.  Push “U” shaped pins into the layers of paper to fasten the layers together.  Then cut the required shape out of all the layers all at one time. 

When finished cutting the shape out, you may want to line the edge with 1mm fibre paper to keep any of the layers of fibre paper showing through.  This dam will not need any kiln wash to prevent the glass sticking to it, unless you want multiple uses and so need to rigidise it with colloidal silica.

You can weight this fibre paper dam down by placing kiln furniture near the edge, all around the shape just as for the fibre board.

Safety in use of refractory fibre is described in Gregorie Glass.

Scroll down to Dusts/Particulates for safety recommendations.