Table of Contents

Varnishes in the Rain 2: Varnish Making, Consistency Testing, and Application

Varnish Making

Name: Tianna Helena Uchacz and Naomi Rosenkranz

Date and Time:

2018.05.17, 10:30 am

Location: Chandler 260 (Making and Knowing Lab)

Subject: Varnish Making

Background

• In previous lab work, we prepared the support and applied the paint layers [add link]

  • Painted oil colors dry enough not to leave color on finger when touched, though not completely dry

  • Decision made to apply varnish to this partially dry paint in order to better simulate the time constraints of creating ephemeral works like banners and painted canvas arches

Aims

• Prepare the 4 varnishes to be tested:

Set-up & materials

• We set up our workspace in the fume hood to include:

  • Hotplate

  • Ceramic plate to hold wooden chopsticks used to stir varnishes

  • Stainless steel bowl with sand to accommodate hot beakers and glass vials

  • Leather gloves to handle hot beakers

  • Digital infrared thermometer

    • Note: difficult to get accurate, uniform reading with this thermometer; all temperatures listed in the observations below are averages or approximations

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Protocol

• We prepared our varnishes according to the following protocol:

1. Sophie Tirat et al., “Reconstructing Historical Recipes of Linseed Oil/Colophony Varnishes: Influence of Preparation Processes on Application Properties,” Journal of Cultural Heritage, Wooden Musical Instruments Special Issue, 27 (2017): S34–43, https://doi.org/10.1016/j.culher.2017.08.001.

2. Making and Knowing Team, “Varnishes for Imitation Jasper - Reference Copy,” https://fieldnotes.makingandknowing.org/pre-2018-Fall/sp18_mk_team_varnishes-for-imitation-jasper-reference-copy.html.

3. No info in Kremer MSDS or in Chemwatch database

Process & Observations

WALNUT OIL + COLOPHONY

• Colophony quite quite easy to crush

• Larger amount than needed crushed to a fine powder using large stone mortar and pestle

• Slightly aromatic

• Sticky powder—it sticks to mortar, pestle, and itself

• It cakes

• It it is not a dry powder

• Using plastic utensils and weigh boat creates a lot of static electricity, and the powder moves around jumps away from the plastic

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• We will be using hotplate D on level 3

• Recipe from Tirat et al calls for heating mixture for 100 min between 170 and 250°C

• DECISION: we will bring walnut oil to 170°C, then add colophony and heat for 60 min

• 10.2 g crushed colophony

• 40.1 g walnut oil

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• 11:18 am walnut oil in beaker on heat

• 11:21 am 40°C; stirred

• 11:22 am 100°C; stirred

• 11:24 am 140°C; stirred

• 11:26 am 180°C; stirred

• Remove from heat

• Add colophony

• Starts to melt in one big lump and begins to dissolve into smaller lumps

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• 11:29 am back on heat

• 11:34 am ~160°C; stirred

• Small and medium lumpy bubbles rising

• 11:37 am 196°C; stirred

• Solution has been getting increasingly darker, from an amber color toward a reddish hue

• Chopstick used to stir has attracted some of the gooey lumps; these can be shaken off in the hot varnish

• 11:41 am decision to not stir for 5 minutes to raise temperature and see if small bubbly, gooey bits will dissolve

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• 11:46 am 214°C; stirred

• Growing darker

• Fewer smaller chunks

• 11:51 am 197°C; stirred

• Turned hotplate up a bit

• 11:55 am 223°C; stirred

• Turned hotplate back to 3; this seems optimal, even with fluctuations

• 11:58 am steam rising

• 12:00 pm darker and reddish

• Still some small gooey dark lumps

• gooey lumps that have congealed on chopstick no longer dissolving

• 12:09 pm 227°C; stirred

• 12:15 pm all remaining gooey dark lumps in the varnish have now dissolved. Decision to leave chopstick in the varnish solution for 5 min to see if those congealed lumps will dissolve; stirred throughout and tried to rub stick against side of beaker to promote dissolution

• 12:17 pm seems like some of the chopstick lump is dissolving, but not much and not qickly

• 12:20 pm chopstick out; much of congealed mass remains

• Wafted smell from varnish: hints of woodiness, umami, hot sauna smell

• Is this just from having left the chopstick in?

• 12:25 pm 218°C; stirred

• 12:30 pm 222°C; stirred

• 12:40 pm 226°C; stirred

• 12:52 pm 208°C; stirred

• 12:59 pm seems like there has been little change to observe in last few minutes

• 1:10 pm 180°C; stirred

• 1:15 pm 189°C

• Removed from heat

• Poured into glass vials

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SILVER FIR TURPENTINE + OIL OF TURPENTINE

• Silver fir turpentine comparatively easy to work with

• Runs, pours readily

• colorless

• Using hotplate E on level 3

• 20.1 g Silver Fir turpentine

• 10.04 g oil of turpentine

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• 11:37 am Silver Fir on heat at 20.9°C

• 11:41 am 177°C; tiny bubbles rising

• Add oil of turpentine

• Heat and stir for ~10 sec.

• Lots of miniscule bubbles forming around the chopstick

• Removed from heat

• Poured into glass vials

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VENICE TURPENTINE + OIL OF TURPENTINE

• Venice turpentine extremely thick; caramel like in consistency; difficult to extract from its jar

• Dark amber-to-ruby color

• So resistant that palette knife blade used to extract it begins to spin in its handle

• We will be using hotplate E on level 3

• 20.39 g Venice turpentine

• 10.00 g oil of turpentine

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• 11:18 am Venice turpentine on heat

• 11:21 am 21°C

• 11:25 am simmering ~170°C

• 11:30 am simmering with small bubbles

• Remove from heat

• Add oil of turpentine

• Stirred to incorporate

• 11:32 am poured varnish into glass vials

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MASTIC + OIL OF TURPENTINE

• Mastic is fragile—it shatters—and is easily broken up by mortar and pestle (medium-sized ceramic)

• Very aromatic, more of a pine smell than colophony

• Smell also slightly citrusy, soapy

• Using hotplate E on level 3

• DECISION: start with ration of 2:1 mastic to oil of turpentine; can expand toward 4:1 ratio if varnish seems too runny

• DECISION: though Venice and Silver Fir turpentines were heated first and then oil of turpentine added when at temp, we will not try to melt mastic directly but heat the oil of turpentine and then add the mastic, watching for signs of excessive volatility of oil of turpentine on heat

• 40.1 g crushed mastic

• 20.2 g oil of turpentine

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• 11:58 pm oil of turpentine on heat; 21°C

• 12:00 pm 74°C; heat waves in liquid, almost bubbling

• 12:01 pm small bubble starting

• 12:02 pm 140°C

• Add mastic

• Remove from heat

• Granular feel as stirring, like running chopstick through bloated and saturated small pieces of sheet gelatin

• 12:03 pm back on heat

• Thinning quickly

• No more resistance

• Stirring in tipped beaker to get residual powdered mastic off sides of beaker

• Much thicker in consistency than any other varnish

• 12:06 pm removed from heat

• Resembles melted honey hair removal wax in its slight crystalline scintillation

• Smells vaguely sweet

• Poured into glass vials

• 12:17 very thick in vial already; little movement when vial is tipped

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Varnish Color Comparison and Consistency Testing

Name: Tianna Helena Uchacz and Naomi Rosenkranz

Date and Time:

2018.05.17, 12:20 pm

Location: Chandler 260 (Making and Knowing Lab)

Subject: Varnish Consistency Testing: Vial Tipping and the “Knife Test”

Aims

• Compare the color and consistency of the finished varnishes

• Assess the utility of the author-practitioner’s “knife test,” as described on fols. 60v, 88r, and 97v

  • “There is no need to put in turpentine, but only its white turpentine oil & mastic pulverized at your discretion, until it has enough body. [...] which one knows when, being placed on a knife in the wind, it does not run.” (fol. 60v)

  • “Test on a very clean knife, & you will know then if it has enough body & if it does not run too much.” (88r)

  • “try it on the knife, and if you see that it has too much body, add in a little turpentine oil, and if it does not have enough, add in mastic, and thus it will be done.” (97v)

Set-up & materials

• For this, we assembled:

  • Vials containing the four varnishes (W + C, ST + TO, VT + TO, M + TO)

  • White paper

  • Palette knife

Protocol

• Line up the varnishes against a background of white paper to better assess color

• The “Knife Test”

  • Dip a palette knife into the vial of ST + TO varnish to coat

  • Blow across the surface of the palette knife to simulate wind

  • Assess the flow of the varnish along the blade

Process & Observations

COLOR COMPARISON

• Against a background of white paper, the newly made vials of varnish ranged in color from dark mahogany (W + C) and maroon (VT + TO) to amber (ST + TO) and honey (M + TO)

• M + TO was comparatively opaque (perhaps due to its thick consistency), while the other three were more transparent

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THE “KNIFE TEST”

• ST + TO varnish was among the thinnest in consistency, yet it still coated the palette knife

• The varnish rippled easily as we blew across the palette knife, suggesting that the varnish, perhaps, did not have adequate “body” (which we interpreted to mean viscosity)

Varnish Application

Name: Tianna Helena Uchacz and Naomi Rosenkranz

Date and Time:

2018.05.17, 12:30 pm

Location: Chandler 260 (Making and Knowing Lab)

Subject: Varnish Application

Aims

• Apply the 4 varnishes in horizontal strips across the previously painted test canvases

• Informally assess and compare the handling properties of the 4 varnishes

Set-up & materials

• Working on a newsprint-covered table, we assembled:

  • 3 previously prepared and painted test canvases

  • 4 varnishes (W + C; ST + TO; VT + TO; M + TO)

  • 1 pencil

  • 4 paintbrushes

  • 4 disposable paper cups

  • Watercolor paper

Protocol

• Divide each canvas into 5 horizontal strips

• Pour each varnish into a paper cup

• Using one paintbrush per varnish type,

  • Test varnish consistency and handling on watercolor paper

  • apply varnishes in the pre-defined horizontal bands or strips across the width of the prepared canvas

• Leaving the bottom strip of each canvas unvarnished

• Leave canvases to dry

Process & Observations

• 12:30: divided painted canvases into 5 horizontal strips using a pencil

  • Each strip cuts across all of the vertically staggered layers of ground and paint

• Poured each varnish into its own disposable paper cup

  • This was straightforward for three of the varnishes (W + C; ST + TO; VT + TO), which were all fairly fluid

  • This was difficult for the mastic varnish (M + TO), which was especially thick and viscous

• Working area is now prepared

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• 12:50 pm: began to apply varnish

  • First applied as test to watercolor paper

  • Next applied to all three canvases

• W + C

  • goes on smoothly

  • Initially flows off relief areas (e.g., raised dots of the oil paint) as it dries

  • Went over these areas a few minutes later with the brush in the opposite direction of application

  • Very yellow in appearance, esp. visible over the lead white; distorts colors beneath

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• ST + TO

  • Very runny

  • Blow test on palette knife (detailed in previous section) shows that varnish is probably a bit runnier than it should be

  • So runny that it drips easily from brush, runs down handle of brush

  • Looks like the varnish is absorbed or evaporates or dries near instantly

  • Very clear in appearance; no visible distortion of colors beneath

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• VT + TO

  • Nice, smooth consistency for application

  • Slightly yellow in appearance, esp. visible over the lead white; slightly distorts colors beneath

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• M + TO

  • So thick it hardly pours from the vial

  • Almost too thick to apply with a brush—firm, short-bristled brush works best

  • Apply in thicker blobs and then pull across paint to even out

  • Difficult to apply; brushstrokes remain visible in this thick varnish

  • Very glossy in appearance

  • Relatively clear in appearance

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• The fifth and final horizontal strip was left entirely unvarnished

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• The canvases were put in the fume hood to dry for 3 hours then moved to table to dry for 4 days, for fear that the air flow through the fume hood might cause more particles to circulate and adhere to the tacky surface than otherwise

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