Conservar Isolating/Finishing Varnish
Conservar Isolating/Finishing Varnish is a colorless, reversible varnish made from aldehyde (Laropal A81) resin dissolved in pure, aromatic and aliphatic solvents with UV stabilizer.
Conservar Isolating/Finishing Varnish is a colorless, reversible varnish comprised of an aldehyde resin (Laropal A81) in an aromatic and aliphatic solvent blend with a UV light stabilizer. It can be used both as an isolating varnish and a final varnish. The varnish can be removed with most of the low-aromatic aliphatic solvents.
Laropal A81 is a urea-aldehyde resin used to make pigment pastes and as a medium in conservation colors. Accelerated aging tests have shown Laropal A81 to be one of the most stable resins available for use as a varnish.* Even after extended exposure to xenon arc lamps, in conditions simulating direct sunlight, the resin remains soluble in a mixture of aliphatic and aromatic solvents similar in proportion in which the freshly prepared varnish dissolves. While some change of the resin occurs after it has aged, this change can be essentially eliminated by the addition of a UV stabilizer,* which is included in Conservar Isolating/Finishing Varnish.
Laropal A81 is insoluble in almost all purely aliphatic solvents, such as odorless mineral spirits, making it an ideal isolating varnish. It can be used with other varnishes applied as a distinct layer, for example, below Conservar Finishing Varnish or other varnishes. Conservar Finishing Varnish remains easily removable without harming the Conservar Isolating/Finishing Varnish in the layer below. Conservar Isolating/Finishing Varnish can be used as a final varnish that is less glossy than Conservar Finishing Varnish.
Compared to natural resin varnishes, such as dammar, Conservar Isolating/Finishing Varnish has a slightly satin-like appearance. It saturates colors as well as dammar but not quite as well as Conservar Finishing Varnish and is considerably less glossy.
Laropal A81 resin in Conservar Isolating/Finishing Varnish has a relatively broad molecular weight distribution (polydispersibility) giving it a pleasant feel or ‘brushability’. When brushing it has enough viscosity to give a feeling of control while it easily spreads out evenly. Its major advantage is its relatively good leveling in a single application without the tendency to sink into matte areas of a painting.
* Rie, E.R. de la, Lomax, S.Q., Palmer, M., and Maines, C.A. 2002. An investigation of the photochemical stability of films of the urea-formaldehyde resins Laropal A81 and Laropal A101. In ICOM Committee for Conservation, 13th Triennial Meeting, Rio de Janiero, 22–27 September 2002, Preprints. R. Vontobel, ed. Vol. II James & James:881–7.
Conservar Isolating/Finishing Varnish is recommended as both an isolating and a final varnish on the following paint films:
All varnishes work differently on casein, distemper, egg tempera, gouache, and watercolor paintings than on acrylic and oil paint because the varnish is absorbed by the paint and/or paper, becoming an integral part of the picture that could cause discoloration as the varnish ages. In addition, varnishes on works created using casein, distemper, egg tempera, gouache, and watercolor cannot be removed because they become an integral part of the paint layer.
To varnish casein, distemper, egg tempera, gouache, watercolor, and drawings, apply Conservar Isolating/Finishing Varnish as an isolating coating on the painting or drawing first, then apply a final picture varnish, such as Conservar Finishing Varnish. In this way, the final varnish can be removed without damaging the painting or drawing underneath. Remember any isolating coating becomes a permanent part of the artwork since it is absorbed by the paint layer.
A four fluid ounce (118 ml) can cover approximately 80 square feet (7.4 square meters).
Prior to actual use, it is very important to test Conservar varnishes on test pieces to understand how they perform and how they alter the surface appearance of your paintings. For best results, apply to a test piece that is similar in composition to the artwork to be varnished. This will help ensure that a successful varnish application will be achieved.
When to Varnish
The best practice is to wait for 6 to 12 months before varnishing with Conservar Finishing Varnish. Oil and alkyd paint films need time (typically months) to polymerize and form a resilient film otherwise a coating added on top of an improperly cured film may cause the layers beneath to swell and loosen.
It may be possible to apply Conservar Finishing Varnish when the thickest areas of your painting are dry through—not touch dry. To determine if your painting is “dry-through”, press into the thickest area of your painting with your thumb at the same time twisting it a full 90° on the paint film. If your painting is on a flexible support, such as stretched canvas, be certain to provide support to the opposite side. The paint is considered dry-through when there is no loosening, detachment, wrinkling, or other distortion visible on the paint surface. This procedure is fully described in the ASTM Standard D1640: Standard Test Methods for Drying, Curing, or Film Formation of Organic Coatings at Room Temperature.
Please note, however, that the more the oil paint is allowed to polymerize or cure the more likely the varnish application will be successful. Always test the application of varnish on test pieces first to determine the suitability of the varnish for your application.
Preparation for Varnishing
Acclimate your painting and varnish materials and tools to the same environment. At least several hours prior to varnishing, place all items, such as your painting, brushes, containers, and Conservar varnish, in the same room. Varnish in a dust-free environment with the least amount of air movement to avoid raising dust.
It is best to brush or spray apply Conservar varnishes. Other methods, such as applying with paint pads, sponging, or rolling, are not recommended, as they may result in foaming, loss of film clarity, non-uniform coverage, excessive film build, sagging, or deposit of materials from the application tool.
Apply with a wide flat, soft-hair brush. Conservar Isolating/Finishing Varnish can be thinned up to 20% with high flash mineral spirits containing at least 20% aromatics. DO NOT MIX WITH WATER. Allow to dry for three days and wipe the varnished surface with a soft, lint-free cloth.
The best way to achieve an even coating of varnish is to apply by spraying. This is particularly true for impasto surfaces. Spraying is also a useful technique for creating a matte surface. The size of the surface to be sprayed will determine the best type of spray equipment to use. Conservar varnishes can be sprayed from an airbrush, airless or air-pressure spray equipment, or refillable aerosol spray can.
To prepare for spraying, make sure all equipment is free of dirt. Work in an area free of dust and dirt and keep work off the ground when spraying. Spray two to four light even coats instead of one or two thicker applications, allowing enough time for drying between coats (1 to 4 hours or until the surface is tack free).
Release the spray trigger when stopping the motion of the sprayer during application in order to avoid a buildup of varnish in one spot. Maintain a uniform distance from the surface, and avoid spraying in an arcing motion. Make straight passes across the work, changing direction once the spray has cleared the edge of the piece being varnished. Slightly overlap the spray pattern with each pass, until the entire passage has been covered.
To achieve a more uniform spray application, turn the painting 90 degrees and apply the subsequent coat perpendicular to the previous one. A typical spray application lays down a film only 1/8 to 1/4 the thickness of a brush coat application. If maximum protection is required of the varnish layer, apply multiple coats.
When applying multiple coats (spray application only), allow 1 to 4 hours in between coats. Inspect the surface for tackiness, which may mean that the coat is not sufficiently dry. Let the varnish cure several days before packing or transporting the painting. During transportation and storage, avoid contacting the surface with packing materials, including glassine, bubble wrap, or any other plastic. NEVER STACK PAINTINGS, whether varnished or not.
Care and Storage
As Conservar varnishes are removable, it is important that they not be painted over. Paint applied over the varnish would also be potentially removable, and would pose a difficult problem in conservation or restoration attempts.
Techniques for Reducing Gloss
There are a number of different ways to reduce the gloss of Conservar varnish:
- Dilute the varnish with additional solvent before using.
- Apply a thin coating. The thinner the coating, the lower the gloss.
- Brush the varnish as it dries. When the varnish is starting to set up, if you continue to brush it then you will microscopically roughen the surface and it will be less glossy.
- Spray apply the varnish.
If the varnished surface of your painting appears too glossy, you can apply a final coating of Conservar Wax. Rub on a thin layer of wax with a soft, lint-free cloth using small circular strokes. Allow the wax to dry overnight for the highest degree of matte. To create a satin finish, allow the wax to dry for about 4 to 6 hours, and then gently buff.
Clean all equipment immediately following the application. Clean brushes with mineral spirits (not odorless mineral spirits), such as a high flash mineral spirits solvent with an aromatic content of at least 20%. To ensure desired results, always make a test piece for your particular application and surface.
Use a clean, soft, lint-free rag dampened with naphtha solvent or mineral spirits (Stoddard solvent). Gently rub the varnished surface and repeat the process until all varnish is removed. Do not use stronger solvents. Allow to dry and reapply Conservar varnish.
The varnish can be thinned to spray application or thin application by brush. Here is the correct solvent for Conservar Finishing / Isolating Varnish: Laropal Solvent.
Laropal is a registered trademark of BASF. Conservar is a trademark of Natural Pigments. Rublev Colours is a registered trademark of Natural Pigments.
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Distillates (petroleum), hydrotreated light
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Conforms to ASTM D4236.