An Investigation into Characteristics of Wax Varnishes on Acrylic Paint Films

Abstract:

This research project explored the properties and characteristics of wax varnishes. It also investigated the interaction of wax varnishes with acrylic paint films and how the appearance of a paint film was altered by this application. The wax varnishes tested include two proprietary brands and two formulations. Tests performed on the samples included observations of handling properties, colorimetry, glossmeter, hardness, tackiness, removability, and analysis using Fourier Transform Infrared Spectroscopy (FTIR).

Introduction:

The goal of this study is to identify an acceptable varnish for acrylic paintings. Acrylic paintings are difficult to varnish due to the porosity and solvent sensitivity of the paint film. Both the properties and characteristics of a wax varnish alone and its interaction with an acrylic paint film are of concern. Several formulas for wax varnishes have been developed using different types and concentrations of waxes. Two proprietary brands of wax varnish and two wax varnish formulations by Rosen and Massey were selected for this study. Collectively, they contain four types of waxes: beeswax, carnauba, ceresin, and microcrystalline wax (Microsere 5906). (See Table 1.) Wax Varnish formulations containing different types of waxes were specifically chosen to diversify the characteristics of the wax varnishes observed.

Table 1. Wax Varnishes to be Investigated.

Experimental:

Sample Preparation •  Sample Set #1: Samples (2 x4 in.) made for observations of handling properties, colorimetry, glossmeter, removability, and analysis using Fourier Transform Infrared Spectroscopy

(FTIR). The colors of Golden and Maimeri acrylic paint used were yellow ochre, ivory or bone black, titanium white, cadmium red medium, and ultramarine. (See Figure 2.) •  Sample Set #2: Samples (2 x15 in.) made for tackiness testing. They were prepared in the same way as the first set of samples using only the color black. •  Sample Set #3: Samples (2 x 4 in.) made in triplicate for hardness testing were prepared on plate glass. The varnish was applied directly on glass cleaned with acetone.

Methods of Testing 1.  Observations of Handling Properties 2.  Colorimetry: Color measurements of all the samples were taken with a Minolta Chroma Meter CR-300 Colourimeter using the CIE L*, a*, b* colour-space before varnishing and after

varnishing. 3. Glossmeter: Readings taken before and after varnishing of samples. 4.  Hardness: ASTM D2134-93, “Standard Test Method for Determining the Hardness of Organic Coatings with a Sward-Type Hardness Rocker.” (See Figure 1.) 6.  Tackiness: Particulate adhesion to varnished samples was observed and recorded with photography. 7.  Removability: FTIR was used to confirm the amount of varnish removability by mineral spirits and turpentine. The cotton swabs were also observed. (See Figure 2.) 8.  Composition of Proprietary Varnishes (FTIR tested, See Figure 5.)

Results: Maimeri Wax Picture Varnish Langridge Wax Varnish Rosen Formula Varnish Modified Massey Formula Varnish

Handling Properties Grey-white, easy application, low viscosity, polishing not needed to achieve a glossy surface.

White, difficult application (sticky), high viscosity, medium pressure to polish.

Pale yellow, easy application, high viscosity, medium pressure to polish.

White, easy application, high viscosity, high pressure to polish.

Colorimetry (ΔE, range for all colors of paint)

0.4 - 3.4 0.3 - 1.5 0.7 - 1.3 0.6 - 1.1

Glossmeter (Δ Gloss, range for all colors of paint)

43 - 65 21 - 66 23 - 52 21 - 47

Hardness (See Figure 6.) 9 hardness value 0 hardness value 7 hardness value 3 hardness value

Tackiness Lowest tack Highest tack, much more than other varnishes.

2nd lowest 3rd lowest

Removability FTIR Spectra Results (See Figures 4 & 6.)

-Mineral spirits= All removed. -Turpentine= All removed.

-Mineral spirits= All removed. -Turpentine= 1 color with minor residues.

-Mineral Spirits= 1 color with samall residues. -Turpentine= 2 colors with minor residues and 2 with no removal.

-Mineral Spirits= 2 colors with small residues. -Turpentine= 2 colors with minor residues and 3 with no removal.

Figure 4. IR spectra of 1:2:2 beeswax, ceresin wax, and carnauba wax in mineral spirits (1:3) or Rosen formula varnish removed with turpentine. *Note: The colors yellow ochre and cadmium red, show no varnish removal in the spectra. All of the other colors show complete or almost complete removal.

Figure 5. IR spectra of proprietary wax varnish: Langridge Wax Varnish. *Note: The Langridge Wax Varnish was listed by the manufacturer to contain beeswax, but in comparison to the spectra of the two have little in common. A better match for this varnish is paraffin wax.

Figure 1. Images of proprietary wax varnishes. Figure 2. Sample preparation for sets 1 & 3.

Varnish Layer

Varnish Layer

Acrylic Paint

Golden Acrylic Gesso

Masonite

Figure 6. Images of the Sward Hardness Rocker and FTIR with Golden Gate ATR.

Conclusions: The results of this study are hoped to contribute both to the fine arts and conservation fields. The handling of wax varnishes depends on the type of wax used and the solvents they are combined with. Wax varnishes are good for contemporary painters that wish to maintain the matteness of acrylic paint and still protect the porous nature of the paint film.

Christina St. Germain Art Conservation Program, Queen’s University

Name/Brand of Wax Varni s h

Formulation Application Techniques/ Recommendations

Maimeri Wax Picture Varnish Beeswax, ketonic resin, white spirit. Can be applied by brush or rag. Rcommended for use with Maimeri Brera Acrylic paint.

Langridge Wax Varnish Refined beeswax, odorless solvent. Can be applied with a lint free cloth. Reccomended for use with Golden Acrylic paints.

Rosen Formula Wax Varnish Beeswax (1 part), Carnauba (2 parts), Ceresin (2 parts), and combine with naphtha until the mixture forms a paste. Ingredients are heated to form a more uniform mixture.

Can be applied by brush or rag.

Massey Formula Wax Varnish (a modified version)

Microsere 5906 (1 part) (Substituted for beeswax in the original formulation), mineral spirits (3 parts). Place in a capped jar until wax dissolves completely into the solvent.

Can be applied by brush or rag.