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Tin Oxide

Alternate Names: Stannic Oxide, Tin(IV) Oxide, Tin Dioxide, SnO2

Oxide Analysis Formula
SnO2 100.00% 1.00
Oxide Weight 150.71
Formula Weight 150.71

Notes

Tin oxide is a white or off-white powder produced by oxidizing molten high grade tin metal. It is typically quite pure, some manufacturers have grades up to 99.999% purity.

Tin oxide has long been used to opacify glazes in oxidation (make transparents opaque) at all temperatures. Hand decorated tin glazed earthenware of the 1700/1800s is the most famous use of tin in glazes (delftware-England, faience-France, maiolica-Italy). While many potters are keeping this tradition alive today most now use zircon based opacifiers instead. Thus any discussion about the use of tin oxide as an opacifier ends up comparing it with zircon products:

-Twice as much zircon is required to produce the same level of opacity.
-Like zircon, tin melts at very high temperatures and thus does not go into solution in typical glaze melts.
-Zircon will stiffen the glaze melt more than tin.
-Zircon will likely produce a harder glaze surface.
-Zircon will reduce the thermal expansion of the glaze more than tin.
-The quality of the white color is different (tin tends to be more of a blue white, zircon a yellowish white).
-Tin is very expensive, this is likely the main reason for its much more limited use as an opacifier today.
-Zircon tends to have less of an effect on the development of metal oxide colors (e.g. tin reacts with chrome to make pink).
-If gloss is an issue, silica might have to be reduced to compensate for the silica introduced by a zirconium silicate opacifier being substituted for tin.
-While there are other products that produce varying degrees of opacity, none are as neutral and non-reactive as tin and zircon. Other opacifiers also tend to variegate the glaze.
-Tin does not normally opacify in reduction firings.

Tin is also a player in the development of ceramic colors, for example chrome tin pinks and maroons. Tin with iron in oxidation makes a warmer shade of brown than zirconium does.

Tin oxide is also a variegator. For example, tin can react with titanium and rutile to to completely transform the color and character of a glaze. Although tin is expensive, very little is required to produce stunning effects in many colored glazes.

Some claim that a little tin (not enough to opacify) will add extra smoothness and shine to many glazes.

Related Information

Zircon, tin oxide, titanium as opacifiers in four base glazes

A grid of fired glaze test samples showing opacifiers perform in four glazes

The body is Plainsman M390. Firing is the cone 6 PLC6DS schedule. Each horizontal row is a commonly-used base glaze. The top one is an MgO matte, the next one down is a calcium matte, row 3 is G2926B glossy and row 4 is Ravenscrag Slip+frit. The two mattes behave very differently from each other with the additions of opacifier. Thickly applying an opacified glaze will obviously affect visual character (column 4). Tin oxide fires whiter than zircon (e.g. Zircopax). If you like the G2934 recipe, consider the G2934Y variant for better melting.

The action of Zircopax vs Tin Oxide at cone 10R

On Plainsman H443 iron stoneware in reduction firing. Notice Tin does not work. Also notice that between 7.5 and 10% Zircopax provides as much opacity as does 15% (Zircon is very expensive).

What tin oxide does to this Floating Blue cone 6 glaze

These two are the same Alberta Slip glaze, except the one on the right has 4% tin added (to the base which is Alberta Slip 80, Frit 3134 20, Rutile 4).

5% tin oxide in a transparent boron cone 6 glaze

This is a 45:27:28 Gerstley Borate:Kaolin:Silica base on a dark firing clay body. But tin oxide will do that in almost any cone 6 clear glaze (use one that fits your clay body).

An original container bag of Tin Oxide

Difference between oxidation and reduction! GR10-C matte on Plainsman H443

Same body, same glaze. Left is cone 10 oxidation, right is cone 10 reduction. What a difference! This is a Ravenscrag-Slip-based recipe on a high-fire iron stoneware. In reduction, the iron oxide in the body and glaze darkens (especially the body) and melts much more. The behavior of the tin oxide opacifier is also much different (having very little opacifying effect in reduction).

G2926B cone 6 transparent with 10% zircon and 5% tin oxide

The body is Plainsman M390. The firing schedule is Plainsman PLC6DS.

G1214Z at cone 6 with 10% zircon and 5% tin oxide

The body is Plainsman M390. The firing schedule is Plainsman PLC6DS.

5% titanium dioxide in G2934 matte, G1214Z matte, G2926B glossy

The body is Plainsman M390. The firing schedule is Plainsman PLC6DS.

G2934 Cone 6 Matte with 10% zircon and 5% tin oxide

The body is Plainsman M390. The firing schedule is Plainsman PLC6DS.

Tin Oxide is expensive, do not waste it by not mixing well

This is a cone 04 glaze on a terra cotta body. Two 300-gram test batches were made. Both have 5% tin oxide added. The one on the left was high-speed propeller-mixed for 10 seconds on a closed container. That was not enough, small agglomerates appear as white specks floating in the glass. The one on the right was mixed for 60 seconds. Now the tin particles, which are incredibly small, have been dispersed and can do their job of opacifying the glaze. Notice that 5% is not quite enough, more is needed.

Partially and fully opacified cone 6 G1214Z matte glaze

This is a calcium matte base (as opposed to the magnesia matte G2934). The clay is Plainsman M390. 5% Zircopax was added on the left (normally 10% or more is needed to get full opacity, the partially opaque effect highlight contours well). 5% tin oxide was added to the one on the right (tin is a more effective, albeit expensive opacifier in oxidation). The PLC6DS firing schedule was used.

How can you test if a different brand of tin oxide will work?

This is a melt fluidity test comparing two different tin oxides in a cone 6 transparent glaze (Perkins Clear 2). The length, character and color of the flow provide an excellent indication of how similar they are.

How do you turn a transparent glaze into a white?

Right: Ravenscrag GR6-A transparent base glaze. Left: It has been opacified (turned opaque) by adding 10% Zircopax. This opacification mechanism can be transplanted into almost any transparent glaze. It can also be employed in colored transparents, it will convert their coloration to a pastel shade, lightening it. Zircon works well in oxidation and reduction. Tin oxide is another opacifier, it is much more expensive and only works in oxidation firing.

Links

Materials Zircon
Materials Zircopax Plus
Materials Zircopax
Materials Zirconium Dioxide
Suppliers HWNano
Suppliers Advance InOrganics
Suppliers Pechiney Chemicals Division
Suppliers Keeling & Walker Limited
Typecodes Opacifier
Opacifiers are powders that turn transparent glazes opaque by various chemical and physical mechanisms (and combinations of mechanisms).
Typecodes Generic Material
Generic materials are those with no brand name. Normally they are theoretical, the chemistry portrays what a specimen would be if it had no contamination. Generic materials are helpful in educational situations where students need to study material theory (later they graduate to dealing with real world materials). They are also helpful where the chemistry of an actual material is not known. Often the accuracy of calculations is sufficient using generic materials.
URLs http://mineral.galleries.com/minerals/oxides/cassiter/cassiter.htm
The Mineral Cassiterite
URLs http://en.wikipedia.org/wiki/Tin_dioxide
Tin Oxide at Wikipedia
Glossary Opacifier
Glaze opacity refers to the degree to which it is opaque. There is more than meets to eye to the subject of opacity control.
Oxides SnO2 - Tin Oxide, Stannic Oxide
Minerals Cassiterite

Mechanisms

Glaze OpacifierAs little as 4-7% can produce brilliant white, although it is more typical to use 8-10% for full opacity. However, be aware that even tiny amounts of chrome in the kiln will volatilize and combine with the tin to produce pink shades.
Glaze VariegationTin reacts with iron in fluid glazes to produce variegated surfaces. A good example is the Albany Slip 85, Tin 4, Lithium 11 glaze for cone 6.

By Tony Hansen


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