OPEN Thinner


GOLDEN OPEN Thinner is a water-based additive optimized for use with GOLDEN OPEN Acrylics and replenishes volatile materials that evaporate during painting. It can also be used as a thin-bodied retarder with other GOLDEN paints and mediums.


GOLDEN OPEN Thinner is a water-based additive designed to thin the consistency of OPEN Acrylics without altering open time, as well as maintain and adjust the workability of colors on the palette. OPEN Thinner can also function as a thin-bodied retarder when used with GOLDEN Heavy Body or Fluid Acrylics. OPEN Thinner contains no binders, does not form a film, and should never be used alone.


Add sparingly to acrylic paints, starting at approximately 10 parts paint to 1 part OPEN Thinner. Maximum addition is 3 parts paint to 1 part Thinner.

OPEN Thinner should not be used in thick applications. Applications of more than 1/16" may result in:

  • Excessively long drying periods
  • Persistently soft, higher tack feel
  • Translucent layers that remain cloudy
Use with GOLDEN OPEN Acrylics
Maintaining Working Properties

As OPEN Acrylics dry, water and other volatile additives evaporate causing the paints to become stiffer with increased brush drag. Adding small amounts of OPEN Thinner replenishes the volatile components, allowing the artist to maintain a long working time and to slow the paint from drying on the palette. It can be difficult to accurately gauge the evaporation rate of volatile ingredients during painting, so add sparingly.

Thinning OPEN Acrylics

OPEN Thinner can be used to lower the viscosity of OPEN Acrylics while preserving maximum working time. Water can also be used for this purpose, and will actually reduce the viscosity of the paint even faster, although it will not preserve the extended open time.

Use with moderation. Over-additions of water or OPEN Thinner can result in a weak, underbound film.

Rewetting of OPEN Acrylic Colors

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"i, apply OPEN Thinner 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.

See our Product Information Sheets for OPEN Acrylic Colors and OPEN Mediums for additional information:

Use With Faster Drying GOLDEN Acrylics

OPEN Thinner may be used as a thin bodied retarder with faster drying GOLDEN Acrylic paints. It should not be used in thick applications of more than 1/16".


Non-Absorbent Palette During Working Sessions

OPEN Acrylics will stay usable on a non-absorbent palette, such as glass or enamel butcher trays, for extended periods of hours and even days without using additional retarders or moisture-retaining inserts by simply covering the palette when not in use. However, depending on the environmental conditions, some thickening of OPEN Acrylics can occur in the course of painting. Some artists have used this natural thickening of the paints as a method of creating a different working consistency without adding a medium.

When using non-absorbent palettes, the following guidelines will help maintain the working time and blendability of OPEN Acrylics:

  • Mist with OPEN Thinner every 1-4 hours to avoid skinning of paint films.
  • Alternatively, mist with water every 15-30 minutes.
  • Thin paint mixtures can also be reopened for 8-12 hrs. by applying any of the OPEN products and brushing back and forth until reactivated.

Left unattended, and under typical ambient conditions, a dollop of paint roughly the size of a small marble could exhibit noticeable surface thickening within 2-4 hrs. However, if misting with OPEN Thinner, similarly sized dollops were still usable after 24 hrs. , with only slight skinning due to a 12 hour period of drying overnight.

Non-Absorbent Palettes Stored While Covered

By simply covering a non-absorbent palette, such as an enameled butcher tray, or placing your palette in an enclosed storage container, even wet mixtures of OPEN Acrylics will stay soft and useable for many days if not weeks. If areas feel tacked up, small additions of OPEN Thinner should easily revive them.

Misting the palette beforehand with either water or OPEN Thinner will further extend these periods as well as help mixtures of OPEN Acrylics with faster drying GOLDEN Acrylics stay useable. Although both OPEN Thinner and water alone are helpful, OPEN Thinner is generally more effective and is our recommendation.

The ability of mixtures of regular GOLDEN and OPEN Acrylic Colors or Mediums to remain useable will be very dependent on the ratios of the mixtures and whether they have been misted with OPEN Thinner or covered with a layer of OPEN Medium. In most cases these should do quite well for a period of days. However, dollops of pure Fluid and Heavy Body Acrylics might become heavily skinned over or not usable during the same period.


Clean tools with soap and water. Keep tools wet while working. 


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.