J. N. (John Norwood) Hoff.

Paint and varnish facts and formulae : a hand book for the maker, dealer and user of paints and varnishes online

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FRANKLIN INSTITUTE LIBRARY

PHILADELPHIA, PA.

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Given bf. LslAt^ Z.L...L L L.tl.a.£l.M.&..£ 7^5



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Paint and

Varnish Facts and

Formulae



BY

J. N. HOFF



A Hand Book for the Maker,

Dealer and User of Paints

and Varnishes



Published by

Central Publishing Company
Newark, New Jersey



New York
D. Van Nostrand and Company

23 Murray and 27 Warren Streets
1905



Copyright 1904

BY

LEMUEL B. OSBORNE.



THE GETTY CENTER
LIBRARY



INDEX.

A

Acid Acetic 6-61

" Sulphurous 84

Adulterations 26-31-35-50

Alcohol, Grain 60

" Wood 61

Alkalies, Action of 85

' ' to remove paint 152

Aluminum Bronze 79

Leaf 112

Amyl Acetate 61

Ammonia 151

Aniline Colors 39-142-162

Anti-f ouling Paints 34

Asphaltum 66-146

B

Banana Liquid 102

Barium Chromate 32

Bathtub Enamel 116

Bathtubs, to Enamel 117

Benzines 59

Berlin Blue 36

Black Boards, Coating for 141

Blacks 27-28

" Charcoal or Soot 27-28

" Ivory or Bone 27-28

Black Enamel 116

Blistering 89

Blooming 87

Blue, Celestial 37

" Chinese 36

" Cobalt 37



-3 G G3£



Blue, Indigo 37

' ' Prussian 36

' ' Ultramarine 35

Boiled Oil 50

" Artificial 171

Bottle Greens 35

British Gum 80

Bronze Greens 35

Bronzing Liquids 102-103

Bronzes 79

" How Made 79

' ' Imported 79

Brushes, Paint 155-156

C

Cadmium Yellow 32

Calcium Carbonate 21

Oxide 21

Sulphate 20

Calcutta Linseed Oil 52

Camphor Oil 175

Carbon 27

Carmine 39-95

Caseine 77-105

Cements 105-106

Paints 77

' ' Priming 94

Castor Oil 131

Ceilings 99

' ' to take spots from 154

Celestial Blue 37

Cements, Pastes and Putties 103 to 106

for Steam Pipes 103

' ' for Metal and Porcelain 104

for Metal Letters on Glass 104

' ' Quick Drying for Iron 104

Stone and Glass 104

Caseine 105

to Unite Glass and Metal 105



Cements, for Glass and Minerals 105

" Paper 106

' ' Caseine for General Use 106

for Steam Pipes 106

Chalking 11-90

China Clay 19

China Wood Oil 52

Chinese Blue 36

Chemical Colors 31

Chrome Greens 33

Chrome Ochre 34

Chrome Yellows 31

Coach Colors 44

Coach Varnish 69

Coal Tar Naptha 60

Coal Tar Pitch 66

Cobalt Blue 37

Cochineal 39

Cold Water Paints 77

Collodion Varnishes 170

Colophony 55

Colors, Complimentary 96

" in Oil, Japan and Water 41

in Water 45

" Used in Water Paints 95

' ' in Decorations 97

" in Oil, Cheap 44

Positive 96

" Predominating 96

' ' Primary 96

Relation to Walls 97

Copperas Reds 26

Cotton Seed Oil 50

Covering Power of Paints, etc 46

Crawling of Paint 89

Cremnitz White 22

Crimson Lakes 39

Crinkling, Peeling and Alligorating 90



D

Damar Varnish 67

Varnish, to Clear 106

Dead Finish Varnishes 170-171

Decorative Effect of Paint 82

Decorative Enamels 113-117

Decorations, Hints for Interior 98-99-100-101

Destruction of Wood Metal and Stone 82-83

Diastase 60

Dotter 49

Drawing or Pulling 87

Dryers, Japan 72

" Lead 71-116

" Liquid 71

' ' Manganese 71

to Test 72-73

Drying Oil, Action of 50-82

Dulling or Flatting 88

Dutch Pink 33

E

Earth Colors, Adulteration of 25-26

Emerald Green, True 34

Emerald Oxide of Chromium 34

Enamels, to Prepare 113-117

Good Grades 114

" Weather Proof 114

" Marine 114

Porcelain White 115

Eosine 38

F

Filler, for Cracks and Crevices 106

Liquid 122

Paste 121-122

" and Stain Combined 124

Fish Oil 50

Flake White 22



Flat White Primer 116

Flax Plant 48

" Seed 48

Floors, to Treat 117-121

Hardwood 118

Painted 118

Varnished 118

Shellaced 119

Waxed 119

to Stain 119

to Oil 120-121

Floor Oils 121

" Paints 149

" Waxes 134

Formulae 102

Fossil Gums 63

Frankfort Black 28

Furnishings 96

Furniture Polishes 148

Varnishes 69

Fusel Oil 61

G

Gamboge 90

Gasolines 59

Gelatine 78

Gilding 110-111

Gilding on Glass 109

" on Iron and Metal 112

Glass to Etch 109

' ' Frosting on 109

" to Gild on 109

Glass Signs, to Back 113

Gloss, Loss of 78

Glues 78

Bone 78

Hide 78

Liquid 108

Waterproof 108



Gold Leaf, Ordinary Ill

" " Artificial Ill

Gold Size 113

Grain Alcohol 60

Graining 125

Pigments Used 125

Tools Required 126-127

Glazing Colors 128-129

Graphite 29

' ' Lubricant ] 33

Greens 33

Bottle 35

Bronze 35

Chrome 33

Emerald 34

Green Oxide of Chromium 33

* ' Emerald Oxide of Chromium 34

" Ultra Marine 35

Gum Resins 64-65-66-67

Zanzibar, Angola, Sierra Leone, Benguela, Kauri
Manilla, Demars, Shellac, Resin, Aspffaltum, Mastic
Sandarac.

Gums, True 79-80

Arabic, Dextrine, British.

Gum Varnish, Cost of 70

Gypsum 20

to Harden 20

use of 20

H

Hard Oil Finish 69

Hints for Interior Decorations 96

Hydraulic Cements 22

I

Indigo 37

Influence of Atmospheric Conditions 82-84

Ink Stains, to Remove 155



Iron, to Preserve 155

Iron Rust, to Remove 155

Isinglass 78

J

Japan Dryer 72

Japan Gold Size 113

K

Kauri Gum . 178

Kalsomines 77

Kalsomining 177

Kerosene 59

L

Lacquer, Bronze and Metal 134

Lakes 38-39

Yellow 38

Red 39

Purple 39

Scarlet 39

Lapis Lazuli 35

Lamp Black 27-28

Lead 71

' ' Antimoniate 32

' ' Carbonate 5

Lead and Oil Paint 74 v

Lead, Sugar of, Dryers 116

Lime 21

Linoleic Acid 94

Linoleum, Treatment of 133

Linseed Oil 48

Process of Manufacture 48

Linseed Oil, Old Process 49

' ' New Process 49

Cold and Hot Pressed 49

Oxidation of 50-71

Adulterations 50

Tests 50



Liquid Slateing 122-123-124

Liquid Wood Fillers 122-123-124

Lubricants 60-129-131

' ' Wagon Grease 132

Patent Wagon Grease 132

Graphite 133

Lubricating Oils 129

' ' Animal, Vegetable and Mineral .... 129-130

Viscosity 130

Congealing and Flash Points 130

Heavy 130

Cylinder 130

" Standard Machinery 130

" Light Machinery 130

High Grade 131

Motor 131

Spindle 131

Extra Cylinder 131

High Grade Cylinder 131

Castor Oil 131

" " Substitute 132

Lard Oil, Substitute 132

M

Machine Paints 146

Malt 60

Manganese 71

Marble, to Polish 148

" to Remove Stains from 154

Marine Paints 34

' ' Enamels 114

Mars Yellow 32

Metallic Brown 23

Metallic Paints 144

" Cheap 144

" Red 145

" High Grade 145

Mineral Black 28

Mineral Oil 17-52-58-129



Mineral Pigments 23-41

Mortar 21

N

Naples Yellow 32

Naptha 59

Nitro-benzole 39



Ochres 23-24-25-32

; ' Artificial Coloring 25

Artificial 32

Cheap 24

English - 24

' French 24

' Golden 25

Gold and Russet Shades 32

: ' Roschelle 24

Oil, Boiled 50

Camphor 175

Castor 130

China Wood' 52

Colza 130

Cotton Seed 17-130

Fish 50

Headlight 132

Lard 129

Lemon 176

Linseed 17-48

Lubricating 60-129-132

Mineral 17-52-58-129

Neatsfoot 129

Olive 130

Palm 130

Poppy Seed 53

Rosin 50-56-57

Signal 132

Solar 60

Sperm 129



Oil, Walnut 53

" Varnish 70

' ' Varnishes 63

Oils, Other Drying 53

Oils and Solvents 48

Oleates and Resinates 71

Orange Mineral 37

Organic Pigments 41

Oxides of Cobalt 37

Oxides of Iron 23

Oxides of Zinc 12

Properties of 13

Adulterations and Tests 14

P

Paint Brushes 155

Care of 157

to Clean 157

Paint, Anti-f ouling 34

Asphaltum 146

Cheap White 140-141

Fireproof 141-142

Flat Interior 93

Flexible 140

Floor 149

for Coating Rough Walls 176

Lead and Oil 74

Marine 34

Paraffine 144

Ready Mixed 137

Silicate of Soda 176

to Clean 154

Transparent for Glass 142

Water Glass 176

Paint Oil Formulae 173

" Oils 171

from Rosin Oil 172

from Resinates 172

from Oxidized Linseed Oil 173



Paint Troubles 89

Crawling 89

Running 89

Drawing and Pulling 89

Loss of Gloss 89

Crinkling 89

Saging 89

Blistering 89

Cracking, Peeling and Alligatoring 90

Chalking 90

Action of Sun on 91

Painting and Decorating 92

" " Exterior 92

Interior 93

Plaster 94

Wood Work 92

Zinc 144

' ' and Varnishing 82

Paints, Paste for Machinery 146

Paraffine Wax * 81

Paris Green 34

Paris White 16-179

Patent Gold Ill

Paper, to Enamel 117

Pastes,Ordinarv 106

" Wall Paper 106

Petroleum Spirits 58

Pigments, Stability of 41

" Tables of Permanency 42

Pinholes in Varnish 87

Pinoline 57

Plaster 20

Plaster of Paris 20

Plumbago 29

Polishing Agents 147

Paint, Properties of S2-84

Life of 84

Covering Power 46

Action of External Agents 84



Polishes, Excellent French 143

for Iron and Steel 143

Polishing Wood Work 94

Poppy Seed Oil 53

Positive Colors 96

Predominating Colors 96

Primary Colors 96

Priming 91-94

Proportion of Oil to Pigments 85

Prepared Floor Wax 134

Putty 17

' ' Joiners 106

" Floor and Crack 108-109

Purple Lakes 39

a

Quercitron Bark 33

Quaker Greens 35

R

Ready Mixed Paints 74-134

Prejudice Against 74

Composition of 75

Pigments Used 75

Cost of 76

Cheap Grades 76

Base 136

Coloring Matter for 137

All Shades, to Make 137

Base White 137

Inside White 135

Outside White 135-136

Solutions for 75-76-135

Facht White 135

Various Colors 137-140

Ready Mixed Paints 134

Apple Green 139

Black 137

Blues Light and Dark 140

Bronze Green 139



Brown, Light and Dark 13S

Buffs 139

Colonial 139

Cream 139

Greens 137

Green Stone, Medium 139

Lavender 139

Leads 138

Lemon 137

Maroon 140

Olives 139

Pea Green 139

Quaker Drab 139

Red 137

Salmon 139

Straws 139

Stone 138

Spruce 139

Tans 139

Vermillion 137

Yellow 137

Red Enamel 116

Red Lakes 39

Red Lead 37-84

Removers, Paint and Varnish 151-153

* ' Ammonia 151

Alkalies 152

" Liquid Removers 152

Removing Whitewash 97

Rolls of Wallpaper, Rule to Determine 98

Rosin 50-55-67

" Light 56

' ' Color, Brands, etc 56

" Oils 57

" Residues 57

" Refined 58

Rubbed Work 93

Running of Paint 89

Rule for Use of Mineral and Vegetable Pigments 29



s

Sandarac G7

Scarlet Lakes 39

Separating of Varnish 87

Shellacs 65

Crude 65

Refined 65

Bleached 66

Shellac Varnishes 166

Shelling 87

Short Oil Varnishes 69

Siennas 23-25

Raw and Burnt 24

Italian 25

Sign Painting Rule 112

Signal Oil 132

Silica 18

in Paint 18

in Fillers 18

Silicate of Alumina 19

" of Lime 94

' ' of Magnesium 20

" of Soda 18-94

Paints 176

Silver Leaf 112

Smalts 81

Smoke Gases 9-84

Soap Stone 20

Solar Oil 60

Solutions 75-76-135

Spirits of Wine 61

Spots, to Remove from Ceilings 154

Spotting or Chilling 87

Stains, Aniline 162

" Oil 163-164

" Spirit 160

" Shingle 165

" Red Brown 163

" Solution for 161



Stains, Yellow Brown 163

4 ' Various Colors to Make 158-160

" Varnish 163-164

11 Water 158

11 Antique Oak 158

" Cherry 159

" Ebony 159

" Grey 159

' ' Mahogany lj? 9

" Mahogany, Light and Dark 158

" Maple 159

" Oak • 15S

" Walnut 158

Stains, Water and Spirit 160

" Blue 16 °

" Blue Black 16 °

11 Brown 16 °

" Brownish Red 160

" Crimson 16 °

" Dark Grey 16 °

11 Greenish 16 °

" Green 161

' ' Greenish Grey 161

11 Yellowish Grey 161

" Cherry Red 161

11 Orange I 61

" Red 161

" Rose Color 161

" Straw Color 161

Solutions 161

Gall Nuts 161

Brazil Wood 161

Fustie 161

Persian Berries 161

Cochineal 161

Indigo 161

Tin 162

Stains, Varnish and Oil 165

Antique Oak 164



Cherry 164

Dark Cherry 164

Green 165

Mahogany 165

Oak 165

Rosewood 165

Walnut 164

Stains, to Remove from Boards 154

" " " " Marble 154

Starch 80

Sticklac 65

Striae 87

Substitutes 132

Castor Oil 132

Lard Oil 132

Linseed Oil 171

" Turpentine 174

Sugar 60-61

Sugar of Lead Dryer 116

Sun, Action of 91

Sweating 86

Sulphate of Cadnium 32

Sulphide of Barium 15

" to Detect 16

of Lead 15

" of Mercury 38

of Zinc 14

Sulphurous Acid 84

T

Talc 20

Tar 61

Terra Alba 20

Testing of Paints 45

Colors 45

Varnishes 73

Tung Oil 52

Turning White of Varnish 88



Turpentine, Spirits of 53-54-55

' ' How Obtained 54

Tests for Purity 55

Drying Properties 54

Turpentine Substitutes 174

Venice 58

U

Ultra Marine Blue 35-36

Ultra Marine Green 35

Umbers 23-25

Burnt and Raw 25

V

Varnishes, Brands of 68

Carriage 67

Ceiling 69

Cheap Black 66

Dead Finish 170

" Gum, Cost, of 70

" Covering Power of 46

Exterior , .67

Flat 171

Furniture 69

Varnish Formulae, Asphaltum 176

Collodion 170

Colorless 168 /

Shellac Grain 167

" Wood 167

" Cheap 167

" Water 167

Varnishes, Special 168

Varnishes, Spirit : . 167

Varnish Gums 64

Interior 67

" Oils 70

Varnishes, Raw Materials 63

Oil 63

Spirit 63



Varnish and Paint Troubles 82

Sweating 86

Shelling 87

Wrinkling 87

Striae 87

Pinholes 87

Spotting and Chilling 87

Drawing and Pulling 87

Separating and Crawling 87

Blowing and Blistering 87

Blooming 87

Turning White 88

Dulling or Flutting 88

Varnish, to Test ,.73

Varnish Formulae, Transparent Brilliant 169

Water Proof 169

Water Proof Paper 169

Vaseline 60

Venice Turpentine 58

Vermillion, True 38

Cheap 38

Venetian Red 21-26

W

Wagon Grease 132

Walls 98

Wall Paper, Hanging of 97-98

Rolls for a Boom 98

Walls, Repapering 97

" Treatment of 97

Walnut Oil 53

Water Proof Glues 108

Water Glass 18-176

" Size 113

Wax Finish for Wood 148

Waxes, Furniture and Floor 134

M Bees 80

Ceresin 81

Carnauba 81



Paraffine 60-81

Polishing 134

White 80

Whiskey 61

Whiting 16-179

White Lead 5

Processes oi' Manufacture 6

Old Dutch 6

Quick Process 6

Pulp Lead 7

Mill Ground Lead 7

Action of Linseed Oil on 9

Action of Other Agents 9-10

Adulterations 10-11

Whitewash 21-177

97

Wild Mustard 49

AYood Alcohol 61

Absolute 62

" Fillers Liquid 122

Quality of 22

Pigments Used 122

Paste 121

Wood Spirit 61

Wood Work, Various Colors, Treatment of .98-99-100-101

" Ash 99

" Brown 99

" Cedar 99

" Chestnut 99

" Cream 99

" Fawn Colored 100

" Ivoory Enamel 100

" Light Golden Oak 100

" Mahogany 100

" Pale Green 100

" Pearl Grey 100

" Silver Birch 100

" Yellow Orange 100



PAINT AND VARNISH
FACTS AND FORMULAE.

CHAPTER I.
WHITE PAINTS AND PIGMENTS.

White Lead.

HTHIS is the most important of all paint forming
dry material, from the standpoint of general,
indeed universal use, it answering most of the
requirements demanded.

Its production cost and selling price is mod-
erate, it can be used as a base to combine with
other pigments, has great opacity, so-called cover-
ing power, mixes readily with linseed oil and tur-
pentine, aids the drying properties of the paint of
which it forms a part, works easily under the
brush when properly mixed, and has reasonable
durability. The last-mentioned property is gov-
erned by the quality of the oil used and the condi-
tions to which the painted surface is exposed.
White lead or basic carbonate of lead of average
quality contains approximately,

Oxide of lead, 86.72

Carbonic acid, 11.28

Water, 2.00

100.00
5



Paint and Varnish Facts and Formulae.

As met with in commerce, it is a heavy pigment
of varying degrees of whiteness, depending upon
the method of manufacture and the care exercised
in its production.

Sometimes a trace of Prussian Blue is added to
increase its appearance of whiteness.

The processes of manufacture in practical
operation may be divided into the slow or so-called
Old Dutch Process, with its modifications, and the
various quick process methods whose name is leg-
ion, few of which, however, are in practical use.

The Old Dutch Process consists in casting the
metallic lead, free from impurities, in the form of
buckles or thin strips of spiral formation ; the lead
thus formed is placed in earthern ware pots so
that it is held or suspended above vinegar or ace-
tic acid which covers the bottom of the vessel.
These pots are arranged in rows and covered with
planks and a layer of dung or spent tan bark. Row
upon row is built up in this manner to form what
is termed a stack. The fermentation of the dung
or tan bark produces sufficient heat to volatalize
the acetic acid, the fumes of which, with the as-
sistance of the oxygen of the air, converts the lead
into basic acetate of lead, which in its turn is con-
verted into basic lead carbonate by the carbonic
acid resulting from the fermenting manure or tan
bark.



Paint and Varnish Facts and Formulae.

The process of conversion requires about three
months. The resulting product is removed, sep-
arated from the metallic lead which may still re-
main to some extent, washed, ground and dried, if
it is to be sold in that form. When to be ground in
oil at the place of manufacture, the drying process
is usually eliminated. The wet or pulp lead in
this case being passed, after screening, into a
pulper. Linseed oil, in proper quantity, is intro-
duced and the mechanical action is such, that the
oil displaces the water contained in the pulp lead
and the now finished product is run into kegs.

This is pulp lead in contradistinction to mill
ground lead made in the old way by grinding dry
lead with linseed oil in stone mills of various types.

Mill ground lead appears to have some favor-
able points to those unacquainted with the pulp
process, but the latter method is so perfect as to
produce lead practically free from water and in
such condition as to " break up " in oil or turpen-
tine much more quickly and easily than will the
mill ground product. Excess of moisture is the
essential point to guard against.

The English method of making white lead is to
convert the metallic lead into litharge, which is
done by oxidizing the metal in a furnace. The lith-
arge in a finely divided state is moistened with lead
acetate solution, placed in closed troughs into



Paint and Varnish Facts and Formulae.

which carbonic acid gas is driven, the litharge be-
ing continually agitated by suitable machinery;
white lead is the resulting product. This lead cov-
ers well, and is considered good. Of the other
quick process methods, the one most largely used
in this country, subjects the metallic lead in a finely
divided state to the action of carbonic acid gas and
acetic acid, in large revolving cylinders.

Another method is to dissolve the lead in acetic
acid, forming a solution of basic acetate of lead
and precipitating this lead in the form of white
lead by introducing carbonic acid gas into the solu-
tion.

The physical properties of white lead produced
by the various processes differs in opacity, fine-
ness, density, and color.

Quick process leads have, as a rule, a crystal-
line formation, giving a tendency to transparency,
while slow process lead (Dutch Process), on ac-
count of the amorphous condition of the substance,
is denser, more opaque, and masks or covers bet-
ter. This opacity is heightened by the pigment be-
ing coarser in grain than the precipitated leads.

Slow process leads are apt to be more or less
off color and to contain impurities unless very
carefully prepared. The quick process leads, in
which the methods are under perfect control, pro-
duce a product, when complete, excelling in white-

8



Paint and Varnish Facts and Formulae.

ness and fineness of texture. This latter property,
the fineness of the particles, makes the lead bulkier
and hence it requires more oil in producing a
workable paint and is another reason why it seems
to cover poorly, The proportion of lead being less
and oil greater.

Of all dry materials used as pigments, white
lead has probably the most action on linseed oil,
the hydroxide of lead combining with a portion
of the oil, to f orm lead soap, which helps to hold the
carbonate of lead in suspension and accounts for
the smooth working qualities and the tough elastic
coat it produces. Too much action between the
particles of lead and oil produces the chalking
tendency of white lead. This is sure to occur
eventually, because the natural tendency of the
lead is to aid the oxygen in the air to oxidize the
oil until the binding properties are entirely de-
stroyed. When white lead is used, however, the
surface left is in better condition for repainting
than that left in the use of most other pigments.

White lead is sensitive to the action of alkalies,
acids, and many substances containing sulphur,
such as sulphuretted hydrogen, which occurs in
coal gases. The sulphur in coal gases causes white
lead to turn black, due to the formation of lead sul-
phide. The drip of rain water from trees or other
foliage also tends to make lead blacken in spots

9



Paint and Varnish Facts and Formulae.

and mildew, particularly where the shade is dense
and little sunlight penetrates. Tinting colors con-
taining sulphides, or linseed oil which is impure, or
which has been bleached and clarified with cer-
tain chemical agents also exercises a bad effect on
white lead, under certain conditions. What ap-
pears to be a dirty blackened condition of the paint
may also be due to dust particles adhering to the
surface of the paint. In this case, washing with a
very weak solution of sal soda will renovate the
surface, the paint underneath being found to be in
good condition. In a small way, the blackening can
be removed by the use of a strong solution of Hy-
drogen Peroxide with 5 per cent, of ammonia
water added, applied with a sponge. This chemi-
cal converts the blackened lead into lead sulphate
which is white. Sunlight also tends to bleach
darkened white lead paint.

White lead is adulterated with lead sulphate, (a
poorly covering white, which mixes badly with oil),
chalk, clay, barytes, gypsum and silex.

These adulterations, in most cases, being neu-
tral pigments, rather increase the durability of the
paint. The objection to these substances is that
they detract from the covering power of the paint,
give it a tendency to crack, and are very much
cheaper than the white lead you are paying for.

Indeed, in the writer's experience, a case was

10



Paint and Varnish Facts and Formulae.

noted where pure lead and oil were used and mil-
dew and blackening occurred, whereas, on part of
the same work, the same lead and oil, with 50 per
cent, paris white added, was applied at the same
time the pure lead was used. The latter work
showed a white, glistening and perfect surface
when the pure lead paint was in a deplorable con-
dition. The only favoring condition given the
adulterated paint, was its exposure to the direct
sunlight, while the other painted work was shaded
by surrounding trees.

It is likely that the neutralizing action of these
cheap pigments do reduce the chemical action of
the white lead on the oil, preventing the binder of
the pigment from perishing so soon as it would
without them, but producing brittleness and lack
of elasticity.

Tests.— Subject the suspected sample of lead to
the blow pipe flame on charcoal. Pure white lead
is readily reconverted into metallic lead without
residue. Any residue present in the form of white
powder is likely to be sulphate of lead or barytes.
Pure white lead is perfectly soluble in dilute nitric
acid and the addition of caustic potash solution
should not form a precipitate. A residue in the
nitric acid solution indicates gypsum, barytes, or
lead suphate.



11



Paint and Varnish Facts and Formulae.

Oxide of Zinc.

White zinc as a pigment is next in importance
to white lead. It is made by strongly heating me-
tallic zinc in fireclay retorts in a reverberatory
furnace. The heat vaporizes the metal, which va-
por is brought into contact with air heated to 300
degrees Fahrenheit. Oxidation results. The oxide
is a very loose flocculent material and is carried
by the hot air into condensing chambers where it is
deposited ready for use.

Zinc white is often prepared directly from its
ores. The roasted ores are pulverized and heated
in a furnace on a bed of coal, and when fully ig-
nited are submitted to a current of air from be-
neath the grate. The vapors formed are kept
strongly heated along with a current of air and led
into condensing chambers. Zinc made direct from
the ores varies in whiteness, but is, for the most
part, a good commercial product, the off grades
produced being sold for other purposes where col-
or is not an object.

It is also produced by the action of lime water
on a solution of zinc chloride. Zinc white takes
much more oil than white lead to make a suitable
paint and, hence, will cover more surface, but is
more transparent and, therefore, requires more
coats to produce the same dense covering given by
white lead. It is practically a neutral pigment in

12



Paint and Vaknish Facts and Formulae.


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Online LibraryJ. N. (John Norwood) HoffPaint and varnish facts and formulae : a hand book for the maker, dealer and user of paints and varnishes → online text (page 1 of 10)