While slow-drying GOLDEN OPEN Paints and Mediums are unique in their working properties, they still dry through the process of evaporation. Factors such as substrate selection, use of mediums and one"s environmental conditions, all play major roles in controlling the drying rate of a paint film.
The first and perhaps easiest way to control working time is through substrate selection.
Absorbent surfaces, such as watercolor paper or gessoed cotton duck canvas, will wick water, retardants, and other additives out of the paint, thereby greatly reducing the working time of the initial layers. To maximize open time when using these substrates, seal the surface with a layer of faster drying acrylic medium, such as GOLDEN GAC 100 or Polymer Medium. If a matte appearance is desired, Fluid Matte Medium or regular Matte Medium can also be used. In addition, applying an initial layer of fast-drying acrylic colors, gels, or pastes will also help seal the surface and can be used to establish a preliminary underpainting or texture. When underlying paint layers are not desirable, the absorbent substrate can be dampened with water or, for even greater working time, a layer of OPEN Thinner or OPEN Acrylic Medium to allow for working wet into wet. This creates a moisture reservoir allowing subsequent paints to blend more readily.
Semi-absorbent substrates, such as gessoed panels, will offer moderate open time compared to the above, while non-absorbent surfaces, like Plexiglas®, offer the most working time.
Use of OPEN Thinner, Medium, or Gel will help maintain or even increase the working time of OPEN Acrylic Colors. However, while OPEN Acrylic Gel and Medium can be added in any ratio, additions of OPEN Thinner should not exceed 3 parts paint to 1 part Thinner. See the following Tech Sheets for full information:
Water and OPEN Thinner can both be used to regulate the loss of evaporatives in the drying paint film. To keep films workable, lightly mist water or Thinner over the paint films and palette as needed. Alternatively, brush small amounts into the paint surface to keep blendable. Always use with moderation. Over-additions of water or OPEN Thinner can result in a weak, underbound film. Because other volatiles will continue to leave the film, only OPEN Acrylic Medium, Gel, or additional layers of OPEN Acrylics, can keep the painting surface workable indefinitely.
See the following Tech Sheet for further information:
OPEN Acrylics can be reactivated for many hours after initial application, allowing for extended periods when multiple layers can be worked and blended into each other. To reopen films before they have fully "locked down", apply OPEN Acrylic Gel or Medium directly to the paint film, brushing back and forth until the paint has been reconstituted.
Even after OPEN paint films have initially set up and become tacky, they can still be reactivated, although more extended or vigorous brushing might be required. Using OPEN Acrylic Gel or Medium for this process will help maintain film integrity and provide maximum working time. While water and OPEN Thinner are also usable, they are very aggressive at reactivating OPEN paint films and should be used sparingly to prevent partially dried films from lifting altogether.
To avoid reactivating underlying paint films, use a light touch when painting over recently worked areas. If one"s methods require more substantial protection, wait for these layers to lock down, which can take several hours or even days depending on application thickness and environmental conditions.
To more quickly isolate layers from potential reactivation by subsequent applications, apply a thin, faster drying coating such as GAC 500, Fluid Matte Medium, or our standard isolation coat recipe of Soft Gel (Gloss) thinned 2 parts gel to 1 part water. However, as mentioned earlier, this will potentially slow the timeline for the development of full inter-coat adhesion.
When faster drying is desired, OPEN Acrylics can be blended with conventional GOLDEN Acrylic products. These mixtures will proportionally adjust the working time and allow for even greater control over the painting process.
There are also major advantages to using these two systems together. Initial layers of GOLDEN Acrylics, Gels, Pastes and Mediums are perfect for creating faster drying underpaintings and textures, which can then be overpainted with OPEN Acrylics, taking advantage of their optimal working time to achieve smoother blended passages, glazes, nuanced edges, and a host of other effects.
Thinner films will set up much faster than thicker ones. This is especially true on absorbent surfaces where very thin, initial coats of OPEN Acrylics can seem to dry or tack up quite rapidly. However, as the painting develops and the surface becomes more sealed, working time will increase as well.
Please note that applications greater than 1/16 of an inch, or about the thickness of a penny, can have excessively long drying periods and remain tacky for an extended period. If greater impasto is desired, use of regular GOLDEN Acrylic Colors and Mediums are strongly recommended.
Environmental factors are major contributors to the actual drying time when working with OPEN. High temperatures, when coupled with low humidity, encourage faster drying while lower temperatures and high humidity can slow the rate. Airflow also impacts drying time, as moving air helps to pull the evaporatives from the paint.
For maximum working time, try to limit airflow across the paint surface as much as possible and maintain a cool environment, like that provided by an air conditioner, paired with a humidifier.
Conversely, the drying time of OPEN Acrylics can be accelerated by increasing airflow, employing the careful use of moderate heat sources such as hair dryers, or maintaining an environment of higher temperature and low relative humidity.
For Plein Air painters control of the environment is much more difficult. For maximum working time, try to position yourself in a shaded area that is protected from the wind. Working earlier or later in the day can also help provide lower temperatures. Lastly, an umbrella can be helpful by providing shade, along with periodically misting one's painting and palette, or covering the paints when not in use.
For additional information about Palette Management, refer to this section of the OPEN Acrylics Tech Sheet:
For additional information on the drying process of acrylic paints refer to the following Application Information Sheet:
The above information is based on research and testing done by Golden Artist Colors, Inc., and is provided as a basis for understanding the potential uses of the products mentioned. Due to the numerous variables in methods, materials and conditions of producing art, Golden Artist Colors, Inc. cannot be sure the product will be right for you. Therefore, we urge product users to test each application to ensure all individual project requirements are met. While we believe the above information is accurate, WE MAKE NO EXPRESS OR IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, and we shall in no event be liable for any damages (indirect, consequential, or otherwise) that may occur as a result of a product application.