White Slip for Brick—

 

English Ball Clay, No. 4 ......................................

40

English China Clay, No. 7 ..................................

16

Ground Flint .......................................................

37

Feldspar ...............................................................

7

 

100

1.61 ounces of liquid blue stain @ 22 1/2 ounces to pint This slip should weigh from 23 to 24 ounces to the pint.

Buff Slip for Brick -

 

Albany Slip Clay ...................................................

5

Buff Clay.........................

23

Calcined Buff Clay ............................................

11

Flint ............................

30

English Ball Clay No. 4 ......................................

27

Felspar .................................................................

4

 

100

Blue Stain—

 

Flint .............................

59.90

Oxide of Zinc ......................................................

8.16

Nitrate of Soda ...................................................

4.73

Oxide of Cobalt ...................................................

27.21

 

100.00

This blue stain should be well mixed and pulverized, placed in a clay vessel lined with flint, and fired at a very high heat, then broken up and ground extremely fine. It should be so fine as to pass through a No. 16 millers' silk bolting cloth easily when in the slip state. It should always be used of such a thickness that one pint of the liquid stain will weigh 22 1/2 ounces. When charging the grinding pan put four ounces of calcined plaster to every six pounds of stain. This will prevent settling. The calcined plaster is any old mold that has been calcined at a bright red heat.

Different shades of blue can be made by adding blue stain to white slip above.

For pearl or very light blue add one-quarter ounce of liquid stain to every pound of dry white slip.

For medium blue add one-half ounce of liquid stain to every pound of dry white slip.

For dark blue add one ounce of liquid stain to every pound of dry white slip.

Shades between these, or darker or lighter, can be made by varying the amount of stain. Grays can be made by mixing buff and blue and adding a small percentage of oxide of chromium.

Sage Green. - White slip, with 12 per cent oxide of chromium added.

Blue Green. - White slip, with 12 per cent oxide of chromium and 2 per cent of liquid blue stain added.

White Glaze, No. 1, for Dipping Wet-

English Ball Clay, No. 4 ......................................

11.69

Felspar ................................................................

41.55

Flint ...........................

31.16

Paris White .........................................................

6.50

Fluor Spar ..........................................................

2.60

Cryolite .............................................................

2.60

Sulphate of Barium ............................................

1.30

Oxide of Zinc ...................................................

2.60

 

100.00

This glaze should weigh from 27 to 27 1/2 ounces to the pint

White Glaze, No. 2, for Dry Dip -

National China Clay ............................................

4.60

English China Clay, No. 7.........

7.19

Felspar .................................................................

41.65

Flint ............................................

31.16

Paris White ........................................................

6.60

Fluor Spar .........................................................

2.60

Cryolite ...........................................................

2.60

Sulphate of Barium .........................................

1.30

Oxide of Zinc....................

2.60

 

100.00

White Glaze, No. 3, for Dry Dip -

English Ball Clay, No. 4..........

4.32

English China Clay, No. 7 .....................................

0.36

Paris White ....................................

7.50

Felspar .....................................................................

41.32

Flint ..............................................

30.00

Fluor Spar ..............................................................

1.27

Sulphate of Barium .................................................

1.27

Cryolite ...................................................................

2.54

Oxide of Zinc .........................................................

2.72

White Lead .............................................................

2.70

 

100.00

White Glaze, No. 4, for Wet Dip -

English Ball Clay, No. 4 .......................................

14.18

Felspar ..................................................................

33.46

Flint ..............................................

18.90

Paris White ..........................................................

20.47

White Lead .........................................................

11.03

Oxide of Zinc .....................................................

1.18

Borax ..................................................................

.78

 

100.00

Chocolate Brown Glaze for Wet Dip -

Albany Slip Clay ........................................

50.38

English Ball Clay, No. 4 ...........................

4.65

Felspar .....................................................

20.15

Flint ..........................................................

9.69

Paris White ...............................................

2.71

White Lead ...............................................

3.1092

Oxide of Zinc .............................................

.7752

Boracic Acid ...............................................

.3876

Cryolite ......................................................

.7752

Fluor Spar .................................................

.3876

Sulphate of Barium ..................................

.3876

Oxide of Manganese ..............

1.5504

Chromate of Iron (Native) .......................

1.5504

Chromate of Lead (Yellow) .....................

3.1092

Red Oxide of Iron .....................................

.3876

 

100.0000

In preparing this glaze weigh out the stains (oxide of manganese, chromate of iron, chromate of lead and red oxide of iron) first and grind extremely fine, then add the other materials. In all glazes it is well, unless the cryolite, fluor spar and sulphate of barium are fine, to put these in the pan first and grind them thoroughly before putting in the other materials.

These slips and glazes will be found to work well, where suited to the contraction of the brick, at the heat at which Albany slip clay fuses into a smooth, almost black glaze, with possibly a slight tendency to show thin on the sharp edges of trials. I prefer the glazes without lead, simply because the lead glazes are so heavy that they are hard to dip without running heavy on the low edge of brick. From experiments made since using these glazes I believe additional oxide of zinc would improve them. The small amount of soluble flux in white glaze No. 4 and in the chocolate brown glaze did not seem to do any harm. In case the color is not satisfactory, from 3 to 10 per cent of oxide of tin added to glaze will probably improve. The lesson in Chapter VI must be borne in mind, and if the slip cracks or shells it must be altered in accordance therewith. The glazes may be softened with lead or a little cryolite, or, preferably, with the artificial mix, made by melting together equal parts of feldspar and borax and substituting this mix for part of the feldspar. In altering glazes never forget, if they work well in all respects but fusibility, to keep the clay the same percentage of the new mixture that it was of the old; that is, if you add a material, add clay also; if you take out a material, take out clay also. The following receipts will work on bodies that shrink lees than the bodies that suit the mixes given above:

White Slip, No. 2, for Wet Dip -

English Ball Clay, No. 4 ............................

12

Flint ...........................................................

25

English China Clay No. 7 ..........................

44

Felspar ......................................................

8

Plaster of Paris ...........................................

11

 

100

White Slip, No. 3, for Dry Dip -

 

English Ball Clay, No. 4 ..........................

10

Flint .........................................................

56

Felspar ....................................................

28

Plaster of Paris .......................................

6

 

100

The glazes given above will work over these slips, Nos. 1 and 4 over Slip No. 2, and Nos. 2 and 3 over Slip No. 3. For work over colored slips it is better to soften the glaze a little. If glaze has partially opaque spots in it when used over colors it requires more flux, and, at the same time, probably less lima

For soft glazes we must resort to lead as a flux. Many of the English writers will state that this is wrong, but our crockery glazes are nearly all lead glazes. We can freeze ice cream in vessels coated with a lead glaze, then boil water and acids in them, and they stand it perfectly through years and years of use. Brick have been in walls for twenty years at least, coated with a lead glaze even softer, and very much softer, than anything I advocate, and they are perfect to-day. These brick have been exposed to the weather during that time. Many glazes that contain no lead are much less reliable than a good lead glaze. The greatest objection to a lead glaze is the danger to the operatives of lead poisoning unless great care is taken. The boys that brush off the glaze from edges after brick are dry should wear sponges over mouth and nose, or some device that will prevent their inhaling the dust I have worked in lead for nineteen years and have never been poisoned thereby, and have not known of a case of lead poisoning from this source that was not directly traceable to gross carelessness.

The following is a lead glaze of about the extreme degree of softness. This will be found reliable where the heat suits it:

Glaze No. 5—

 

English Ball Clay, No. 4...........

11

Felspar ........................................................

30

Flint ...........................

15

Paris White ................................................

8

Oxide of Zinc ..........................................

4

White Lead ............................................

32

 

100

This glaze will fuse at about the heat where Albany slip clay becomes a brown semi-glaze. It cannot be put on all clays by the single fire process. The clay must be one that burns hard at a low heat, so that the clay will be burned clay and have some strength before the glaze begins to melt In altering this glaze retain the full percentage of clay, as this seems to be what makes it applicable to the single fire process. Without the clay in it the glaze will draw up in drops. By mixing this glaze with glazes Nos. 1 and 4 different degrees of fusibility can be obtained. I must repeat my advice above, however - get along without lead, if possible; try to get the fusibility with the artificial mix so often mentioned.