Cleaning Painted Surfaces

This study offers practical guidance on selecting effective, controlled cleaning methods for varnished and unvarnished paint surfaces. Grounded in extensive experience, it emphasizes aqueous cleaning for 19th-20th-century objects but presents principles applicable across diverse materials and eras.

There is no layer of a painting where we are fully satisfied with our present understanding of its material structure, and its deterioration over time. Most research carried out today into the materials of paintings concentrates on their properties in order to further understand the consequences of conservation treatments – both immediate and long term – and the effects of earlier treatments. This book contributes significantly to the selection of appropriate and controllable cleaning methods for varnished and unvarnished paint surfaces. It is a distillation of many years’ experience of formulating a cleaning treatment for a given object. While the case histories describe nineteenth- and twentieth-century paintings and furniture exclusively, and may emphasise the cleaning of never-varnished surfaces to an extent unusual in some conservators’ experience, the general principles are applicable to the surface cleaning of both traditional and modern paint media. These, in fact, may be found on sculptures, ethnographic materials, and even textile and paper supports, as well as on paintings, gilded surfaces and furniture. Aqueous methods are certainly worth considering for those surfaces which cannot be cleaned safely by the more traditional methods based on the use of solvents.

Acknowledgements

Foreword

1. Introduction

1.1 Introduction

1.2 Adhesion of soils

1.3 Traditional aqueous methods

2. Acids and bases

2.1 Chemical equilibria

2.2 Law of Mass Action

2.3 Acids and bases and the definition of pK and pH

2.4 Hydrolysis

2.5 Buffers

2.6 Acid-base titrations

2.7 Solubility product

Case History 2.1: James Peale, Portrait of Mary Morris Jones (oil on canvas, early nineteenth century)

Case History 2.2: F. Schoonover, The Prodigal Father (oil on canvas, 1932)

3. Surfactants and affinity surfactants

3.1 Surface activity and surfactants

3.2 Structural classification of surfactants

3.3 Properties of solutions containing surfactants

3.4 Critical micelle concentration (CMC)

3.5 Micelle size: aggregation number

3.5 Micelle size and charge

3.6 Krafft point: temperature versus solubility of surfactants

3.7 CMCS for nonionics

3.8 Affinity surfactants

Case History 3.1: E. Von Liebrach, Winterscape: Skating on the Pond (oil on canvas, nineteenth century)

Case History 3.2: Unattributed, Venetian Canal Scene (oil on canvas, nineteenth century)

Case History 3.3: Dean Wolstenholme the elder, The Death (oil on canvas, early nineteenth century)

Case History 3.4: Unattributed, German Student Model Violin Bow (composite object, pre-World War ll)

Case History 3.5: C. F. Ryder, Paxsons Hollow (oil on canvas, nineteenth century)

4. Detergents and detergency

4.1 Detergency

4.2 Mechanisms of detergency

4.3 Laundry detergent compositions as models for detergency

4.4 Evaluation of detergency

4.5 Adsorption of surfactants on soil and substrate surfaces

4.6 Surfactant adsorption as a function of CMC, pH, and counter-ion concentration

4.7 Detergent systems design

Case History 4.1: Joan Brown, Kitchen Still Life (oil on canvas, 1964)

Case History 4.2: Unattributed, Corner Cupboard (composite object, Pennsylvania 1830-1840)

4.8 Detergency in non-aqueous systems

Case History 4.3: Unattributed, Massachusetts Hinged Writing Desk (composite object, 1750-1780)

Case History 4.4: William Naismith, Pastoral Landscape (oil on canvas, nineteenth century)

Case History 4.5: Frederic Remington, In Defense of the Barricade (oil on canvas, 1889)

Case History 4.6: Unattributed, Tilt-top Tea Table (composite object, Philadelphia c.1765)

5. Emulsions

5.1 Emulsions: definition

5.2 Hydrophile-lipophile balance (HLB) number

5.3 Macroemulsions

5.4 Phase inversion temperature (PIT)

5.5 Cloud point

5.6 A ternary system: xylene/water/Triton X-100

Case History 5.1: Unattributed, Polychrome Trade Sign, Bust of George Washington (composite object, late nineteenth century)

5.7 Microemulsions

Case History 5.2: Unattributed, Gilded Frame (composite object, nineteenth century)

Case History 5.3: Elmer Garnsey Architectural Decorative Paint (early twentieth century)

6. Chelation

6.1 Chelation: definition

6.2 Metal displacement equilibria

6.3 Estimation of ion concentrations on paint films

Case History 6.1: Albion Bicknell
Painting of a Prize Cow (oil on canvas, late nineteenth century)

6.4 Chelate-chelate exchange equilibria

Case History 6.2: J. L. Hansen, Portrait of Hannah Holbrow (oil on canvas, 1842)

6.5 Metal buffering

Case History 6.3: William Mason Brown, Landscape: View of a River (oil on canvas, c.1865)

7. Enzymes

7.1 Enzymes

7.2 Classification of enzymes

7.3 Active sites on enzymes

7.4 Enzyme kinetics

7.5 Temperature and pH effects on enzyme reaction rates

7.6 Enzyme purification and isolation

7.7 Enzymes important to conservation

Case History 7.1: Jacob Eichholtz, Portrait of Anne Ross Hopkins (oil on canvas, nineteenth century)

Case History 7.2: Unattributed. Christ Washing the Feet of the Disciples (oil on canvas, nineteenth century)

Case History 7.3: Unattributed
Wallpaper Fragment. Corbett-Sharp House, Odessa, Delaware (paper, early nineteenth century)

Case History 7.4: Frederick Sandys, Portrait of Miranda (oil on panel, nineteenth century)

7.8 Other enzymes of special note

8. Clearance

8.1 Clearance: an introduction

8.2 Properties of paint surfaces

8.3 Properties of varnished surfaces

8.4 The design of cleaning systems with clearance in mind

8.5 Residual material remaining after cleaning

8.6 Substitution of less toxic materials for cleaning

8.7 Specific clearance conditions

Appendix 1: Examining and staining paint cross-sections

A1.1 Carbohydrates

A1.2 Proteins

A1.3 Lipids, oils and fats

A1.4 Resins

Appendix 2: Suppliers of materials

Sigma Chemicals

Ethomeen and Carbopol products

Micromesh polishing materials

Shellsol T (mineral spirits)

References

Index,

Acknowledgements

Foreword

1. Introduction

1.1 Introduction

1.2 Adhesion of soils

1.3 Traditional aqueous methods

2. Acids and bases

2.1 Chemical equilibria

2.2 Law of Mass Action

2.3 Acids and bases and the definition of pK and pH

2.4 Hydrolysis

2.5 Buffers

2.6 Acid-base titrations

2.7 Solubility product

Case History 2.1: James Peale, Portrait of Mary Morris Jones (oil on canvas, early nineteenth century)

Case History 2.2: F. Schoonover, The Prodigal Father (oil on canvas, 1932)

3. Surfactants and affinity surfactants

3.1 Surface activity and surfactants

3.2 Structural classification of surfactants

3.3 Properties of solutions containing surfactants

3.4 Critical micelle concentration (CMC)

3.5 Micelle size: aggregation number

3.5 Micelle size and charge

3.6 Krafft point: temperature versus solubility of surfactants

3.7 CMCS for nonionics

3.8 Affinity surfactants

Case History 3.1: E. Von Liebrach, Winterscape: Skating on the Pond (oil on canvas, nineteenth century)

Case History 3.2: Unattributed, Venetian Canal Scene (oil on canvas, nineteenth century)

Case History 3.3: Dean Wolstenholme the elder, The Death (oil on canvas, early nineteenth century)

Case History 3.4: Unattributed, German Student Model Violin Bow (composite object, pre-World War ll)

Case History 3.5: C. F. Ryder, Paxsons Hollow (oil on canvas, nineteenth century)

4. Detergents and detergency

4.1 Detergency

4.2 Mechanisms of detergency

4.3 Laundry detergent compositions as models for detergency

4.4 Evaluation of detergency

4.5 Adsorption of surfactants on soil and substrate surfaces

4.6 Surfactant adsorption as a function of CMC, pH, and counter-ion concentration

4.7 Detergent systems design

Case History 4.1: Joan Brown, Kitchen Still Life (oil on canvas, 1964)

Case History 4.2: Unattributed, Corner Cupboard (composite object, Pennsylvania 1830-1840)

4.8 Detergency in non-aqueous systems

Case History 4.3: Unattributed, Massachusetts Hinged Writing Desk (composite object, 1750-1780)

Case History 4.4: William Naismith, Pastoral Landscape (oil on canvas, nineteenth century)

Case History 4.5: Frederic Remington, In Defense of the Barricade (oil on canvas, 1889)

Case History 4.6: Unattributed, Tilt-top Tea Table (composite object, Philadelphia c.1765)

5. Emulsions

5.1 Emulsions: definition

5.2 Hydrophile-lipophile balance (HLB) number

5.3 Macroemulsions

5.4 Phase inversion temperature (PIT)

5.5 Cloud point

5.6 A ternary system: xylene/water/Triton X-100

Case History 5.1: Unattributed, Polychrome Trade Sign, Bust of George Washington (composite object, late nineteenth century)

5.7 Microemulsions

Case History 5.2: Unattributed, Gilded Frame (composite object, nineteenth century)

Case History 5.3: Elmer Garnsey Architectural Decorative Paint (early twentieth century)

6. Chelation

6.1 Chelation: definition

6.2 Metal displacement equilibria

6.3 Estimation of ion concentrations on paint films

Case History 6.1: Albion Bicknell; Painting of a Prize Cow (oil on canvas, late nineteenth century)

6.4 Chelate-chelate exchange equilibria

Case History 6.2: J. L. Hansen, Portrait of Hannah Holbrow (oil on canvas, 1842)

6.5 Metal buffering

Case History 6.3: William Mason Brown, Landscape: View of a River (oil on canvas, c.1865)

7. Enzymes

7.1 Enzymes

7.2 Classification of enzymes

7.3 Active sites on enzymes

7.4 Enzyme kinetics

7.5 Temperature and pH effects on enzyme reaction rates

7.6 Enzyme purification and isolation

7.7 Enzymes important to conservation

Case History 7.1: Jacob Eichholtz, Portrait of Anne Ross Hopkins (oil on canvas, nineteenth century)

Case History 7.2: Unattributed. Christ Washing the Feet of the Disciples (oil on canvas, nineteenth century)

Case History 7.3: Unattributed; Wallpaper Fragment. Corbett-Sharp House, Odessa, Delaware (paper, early nineteenth century)

Case History 7.4: Frederick Sandys, Portrait of Miranda (oil on panel, nineteenth century)

7.8 Other enzymes of special note

8. Clearance

8.1 Clearance: an introduction

8.2 Properties of paint surfaces

8.3 Properties of varnished surfaces

8.4 The design of cleaning systems with clearance in mind

8.5 Residual material remaining after cleaning

8.6 Substitution of less toxic materials for cleaning

8.7 Specific clearance conditions

Appendix 1: Examining and staining paint cross-sections

A1.1 Carbohydrates

A1.2 Proteins

A1.3 Lipids, oils and fats

A1.4 Resins

Appendix 2: Suppliers of materials

Sigma Chemicals

Ethomeen and Carbopol products

Micromesh polishing materials

Shellsol T (mineral spirits)

References

Index

• By (author) Richard Wolbers

"Wolbers's contribution to cleaning methodology is the most significant of the last century. This book will bring his approach to a wider audience, and it will be interesting to see whether, as a result, gels will be used more often as an alternative, or even as a substitute, for cleaning using more traditional techniques." Studies in Conservation 46 (2001) 221 "[Cleaning Painted Surfaces] is crammed with useful information and inspiring insights, and it is probably the most thorough book ever written on a conservation issue which continues to cause controversy." The Strad Magazine (February 2002) 205
—

Wolbers's contribution to cleaning methodology is the most significant of the last century. This book will bring his approach to a wider audience, and it will be interesting to see whether, as a result, gels will be used more often as an alternative, or even as a substitute, for cleaning using more traditional techniques.

—

[Cleaning Painted Surfaces] is crammed with useful information and inspiring insights, and it is probably the most thorough book ever written on a conservation issue which continues to cause controversy.

—