Volumetric blending is a process whereby blend samples (individual recipes in a blend) are created by dispensing from bulk recipes in liquid form.

For example a line blend may be made by mixing a large amount of the A and B corner recipes so that the recipes in between the corners can be made by taking some of the liquid recipe from the bulk Corner A and some from the Corner B recipe and mixing them together.

Volumetric blending will only work if we have the same weight of dry materials in the same volume of liquid for each of the corner recipes. If this is not the case then the glazes in the pottles will not relate to the individual recipes for each pottle listed on your worksheet or recipes printouts.

Fig.1 shows pottles laid out for the making of a 7 sample line blend. The worksheet data printout provided by Matrix (Fig.2) will give us the bulk recipes for Corner A and B, the minimum volume for each bulk recipe and the Millilitres per Sample blending chart.

Fig.1 Pottles laid out for a 7 sample line blend.

Fig.2 Worksheet printout for a 7 sample line blend.

Steps for Mixing and Dispensing a Line Blend

1. Batch Corner recipes are weighed and mixed with a minimum amount of water sufficient to get the recipe through a seive. Try not to leave behind too much of the glaze materials in the suive or on the brush.
   
   
2. Each bulk recipe can be poured into a plastic measuring jug where water can be added if necessary to bring the volume to a minimum of 350 mls. The volumes of the bulk recipes can be more than 350 mls as long as they are the SAME before creating the intermediate recipes in the blend. 350 mls for each bulk recipe is the minimum needed to make a 7 step line blend with 96 mls in each sample recipe. If you end up with too much water in the bulk recipes making them too runny they can usually be left to stand overnight during which time the glaze materials will sink to the bottom of the containers. Excess water can decanted of or drawn off using a syringe
   
   
3. Pottles which will hold 96 mls are laid out and labeled with numbers (Fig.1).
   
   
4. Bulk recipes are thoroughly stirred and kept that way throughout the next steps.
   
   
5. A 60 ml veterinary syringe is used to draw off samples from Bulk Recipe A and Bulk Recipe B in accordance with the MILLILITRES PER SAMPLE chart on the worksheet printout.(Fig.2) e.g
   
   
   • to make recipe #2 we would draw off 80 mls of glaze from Bulk Recipe A using the syringe and squirt it into pottle #2 then draw off 16 mls of glaze from Bulk Recipe B using the syringe and squirt it into the same pottle #2
     
     
   • to make recipe #3 we would draw off 64 mls of glaze from Bulk Recipe A using the syringe and squirt it into pottle #2 then draw off 32 mls of glaze from Bulk Recipe B using the syringe and squirt it into the same pottle #2 ... and so on to blend all of the recipes.
     
     
6. While you are mixing the blends using measures from the bulk recipes it is wise to be very sytematic and tick off each completed measure after squirting it into a pottle. This is particularly important when mixing a large blend such as a Standard Recipe Grid.
   
   
7. The blended recipes are now ready for applying to whatever clay surface you use for test firing. If you are dipping tiles you may sometimes find the blend recipes too runny or too thick. AFTER THE RECIPES HAVE BEEN BLENDED it is ok to decant off some water (the next day) or add some water to each of the blended recipes in the pottles.

Mixing Triaxial and Biaxial Blends

The same system as that described above is used for mixing triaxial or biaxial blends. The only difference is that there will be more bulk recipes to mix and more small pottles to prepare before commencing the blending process.

Important Ponts to Note

• take care not too leave glaze materials behind in the seive or on a brush when preparing the bulk recipes.
  
  

• the volume of each of the wet bulk recipes must be the same before commencing the blending

• bulk recipes must be kept well stirred during the blending process particularly when mixing large blends.

• samples taken from bulk recipes for each of the blended recipes must be carefully measured and checked off on the blending chart.

• each of the blend recipe pottles should be well shaken before application to clay surfaces of the dipping of test tiles.
  
  
• if you are using loose test tiles number them carefully and stand them in front of the pottle into which they will be dipped.

Using the Individual Recipes Generated By Matrix.\

The worksheet printout or the Recipes and Formulae printout has a recipe for each of the recipes in the blend. After firing the blend you will want to evaluate the results and perhaps mix up larger amounts of the recipe for the sample number which interests you.

It is always wise to mix up and test fire a small sample (say 500 grms) of the individual recipe before committing yourself to using the glaze on important pieces.

The recipe and formulae printout will also have coefficients of expansion and Al:Si ratios for each recipe. You may wish to spot test some of these recipes rather than mix the whole blend.

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