OPEN Acrylic Medium

Acrylic Gel & Paste Mediums

OPEN Mediums
OPEN Acrylic Gel (Gloss)
OPEN Acrylic Gel (Matte)
OPEN Acrylic Medium (Gloss)
OPEN Acrylic Medium (Matte)

OPEN Mediums are used to extend and to modify the viscosity and transparency of OPEN Acrylics while maintaining their maximum working time. OPEN Mediums may be blended with GOLDEN Acrylics, Medium and Gels, with the open time of the resulting mixtures being proportionately increased.

PRODUCT DESCRIPTION

GOLDEN OPEN Acrylic Gel (Gloss) and OPEN Acrylic Medium are formulated with 100% acrylic polymer dispersion and have been engineered to have the same optimized working time as OPEN Acrylic Colors, making them ideally suited for use with this line of paints. Like OPEN Acrylics, OPEN Mediums will also stay wet on the palette for extended periods without skinning over.

OPEN Mediums can be used to extend paint, regulate transparency, create glazes, increase gloss, reduce viscosity or improve adhesion and film integrity.

OPEN Mediums are fully compatible and may be blended with most other GOLDEN Acrylics, Mediums and Gels, with the open time of the resulting mixtures being proportionately reduced.

OPEN Acrylic Gel (Gloss) is supplied in the same consistency as OPEN Acrylic Colors and is used to extend the paints while maintaining working properties.

OPEN Acrylic Medium (Gloss) is formulated to a lower viscosity than OPEN Acrylic Colors and is used to maintain properties when a more fluid mixture is desired to increase flow.

PRODUCT APPLICATION

Using with OPEN Acrylics

Mix any quantity of OPEN Gel or OPEN Medium with OPEN Acrylics in order to extend the paint or modify its sheen, viscosity, or transparency. If one experiences a change in viscosity while using, small additions of OPEN Thinner will help maintain the expected working properties. See the OPEN Thinner Product Information Sheet for more information.

Mixtures with OPEN Acrylics can be blended for extended periods, allowing one to develop smooth transitions and to manipulate edges. Over time, thin applications will pass through several stages where the paint will begin to slowly set up and its tack increases. During this time, which can last for many hours, subsequent applications of any OPEN products or water can continue to reopen layers and allow one to continue blending and developing complex passages and fine details.

OPEN Acrylic Colors, Gel and Medium are best used in thin layers. Applications of more than 1/16 will result in:

Excessively long drying periods
Persistently soft, higher tack feel
Translucent layers that remain cloudy

For thicker applications and texture, faster drying GOLDEN Acrylic Colors, Gels or Mediums are strongly recommended.

Layering OPEN With Faster Drying Acrylic Products

It is best to allow films containing OPEN Gel or Medium to dry fully before applying faster drying layers on top. Since volatile materials in OPEN evaporate slowly, faster drying layers can easily entrap these materials and delay the time when the layers will fully adhere to each other. While ultimately all layers will coalesce and develop full adhesion, quickly interleafing faster and slower drying layers can cause some of those layers to display early adhesion failure if pulled on, as can happen in hard-edge techniques that use masking tape.

Do not apply thick films of faster drying gels on top of applications of OPEN Acrylics, Gel, or Medium without waiting for a minimum of two weeks after being touch dry. This extended period is needed to avoid the volatile materials that might still be evaporating from the underlying materials from causing these faster drying gel applications from remaining cloudy or hazy.

Rewetting 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 downⁱ, apply OPEN 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 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.

Using With GOLDEN Acrylic Colors, Gels and Mediums

OPEN Gel and Medium may be mixed in any ratio with nearly the full range of GOLDEN Acrylic Colors, Gels, Pastes, and Mediums. Resulting drying time will be dependent on the ratio. For exceptions please see the section:
Ongoing Research

Mixtures with standard acrylic products should follow the same guidelines as OPEN Acrylics and Mediums, including keeping applications thin. See our Product Information Sheet on OPEN Acrylic Colors for more information.

There are also major advantages to be gained by using these two systems together. 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.

Thinning

OPEN Gel and Medium can be thinned and extended with OPEN Thinner, water, or faster drying GOLDEN Mediums. For most painting techniques the following guidelines are recommended:

OPEN Thinner will reduce the viscosity while still preserving the optimal working time. Since OPEN Thinner contains no binders, limit additions to a maximum 3:1 ratio of 3 parts OPEN Gel or Medium to 1 part OPEN Thinner to maintain film integrity.
Water will very rapidly reduce the viscosity but will not preserve the extended open time. To maintain film integrity limit additions to a maximum 2:1 ratio of 2 parts OPEN Gel or Medium to 1 part water.
Faster drying GOLDEN Mediums can be added in any ratio to OPEN Gel and Medium to modify viscosity, but will lower the open time in proportion to the ratio.

For washes and stains on porous and absorbent grounds, one may exceed the above ratios, although the resulting paint films will become increasingly fragile and water sensitive. To later preserve these works, they will need to be properly framed and protected in ways similar to watercolors, or the surface will need to be consolidated with a layer of acrylic medium or an isolation coat prior to varnishing.

Modifying Viscosity, Opacity and Sheen

As noted above, OPEN Thinner will alter the viscosity and flow of OPEN Gel and Medium while maintaining their optimal working time. Water will rapidly reduce the viscosity but will not preserve the extended open time.

Faster drying GOLDEN products can also be used, keeping in mind that these mixtures will reduce the overall drying time of the resulting blend. To increase opacity, mix with GOLDEN Pastes. To alter sheen, use GOLDEN Matte Gels and Mediums. Alternatively, the sheen can be modified at the level of a topcoat or varnish.

Use OPEN Gel, Medium, and Thinner to alter the viscosity, transparency, and flow of OPEN Acrylics while maintaining their optimal working time. OPEN Gel and Medium can be added in any ratio; while additions of OPEN Thinner should not exceed 3 parts paint to 1 part Thinner. As most OPEN Acrylics will dry to a satin-like sheen, mixing with OPEN Gel and Medium will also increase the overall gloss.

Faster drying GOLDEN products can also be used, keeping in mind that these mixtures will reduce the overall drying time of the resulting blend. To increase opacity, mix with GOLDEN Acrylic Colors or GOLDEN Pastes. To alter sheen, use any of the GOLDEN Gels and Mediums. Alternatively, the sheen can be modified at the level of a topcoat or varnish.

DRYING TIME

Under ambient conditions of 70ºF/21ºC and 30% RH, OPEN Gel and Medium will provide, on average, a working time that is 10 times longer than the usual acrylic gels and mediums. Below is a table showing some test results on gessoed cards:

Film thickness: 6 mil (roughly equivalent to a heavy brushstroke)

	Wetⁱⁱ	Workableⁱⁱⁱ	Can still be reopened^iv	Touch dry^v	Locked downⁱ
OPEN Acrylic Gel	30 min.-1 hr.	1-3 hrs.	~12 hrs.	24+ hrs.	14+ days
Soft Gel	<5 min.	~ 10 min.	n/a	~30 min.	3+ days.
OPEN Acrylic Medium	30.-60 min.	1-3 hrs.	~12 hrs.	24+ hrs.	14+ days
Polymer Medium	<5 min.	~ 10 min.	n/a	~30 min.	3+ days
Acrylic Glazing Liquid	10-20 min.	15-40 min.	n/a	~1 hr.	5+ days

To accelerate drying time, OPEN Gel and Medium may be blended with faster drying GOLDEN Acrylic products. The corresponding drying time will be dependent on the ratio of the mixture.

CLEANING

Clean-up of brushes, tools, and palettes are far easier when using OPEN than traditional acrylics. With the extended open time, brushes that have been unintentionally left out for many hours can still be readily cleaned. Should the paint have tacked up or become stiff or even recently dried to the touch, soaking the brushes in OPEN Thinner will facilitate the removal of the paint. Afterwards, use soap and water to complete cleaning, repeat if necessary.

SUBSTRATES AND POTENTIAL S.I.D. ISSUES

Since OPEN Gel and Medium are extremely slow drying, using them on substrates that contain high levels of water soluble impurities, such as many hardboard wood panels commonly referred to as Masonite^®, leads to concerns of S.I.D. (Support Induced Discoloration). This is especially true if working with thicker translucent layers or ones that have been kept wet for extended periods, where moisture has ample time to penetrate into these substrates and allow impurities to be solubized. Because of this, we strongly recommend using MDO (Medium Density Overlay) or furniture grade Birch plywood if wanting to paint on a wood substrate. In addition, we recommend the following as the optimal system for preparing wood supports for use with OPEN Acrylics, Gel, and Medium:

BEST: 3 coats of GOLDEN Gloss Medium followed by one or more coats of GOLDEN Gesso
GOOD: 3 coats of GOLDEN GAC 100 followed by one or more coats of GOLDEN Gesso
NOT RECOMMENDED: Shellac-based primers or sealers.

For more information see our Just Paint article, OPEN Acrylics, Shellac, and SID

VARNISHING

In order to assure all volatile materials have completely evaporated, work using OPEN Gel and Medium should dry for a minimum of 30 days prior to application of a varnish, and a minimum of 2 weeks before application of an isolation coat. Paintings using thicker films, or a large number of layers applied in a relatively short period, may require a longer drying time.

For more information please refer to the following Application Information Sheet:
Varnish Application Guidelines

EXTERIOR MURALS AND SCULPTURES

We Do Not Recommend the use of OPEN products for any exterior applications where the extended dry time and additional period of water-sensitivity could pose problems that are otherwise not a concern in an indoor setting. However, OPEN Acrylics can be used for interior murals and sculptures meant solely for indoor settings.

ONGOING RESEARCH

Due to the newness of this medium, some applications and uses of the OPEN Gel and Medium have yet to be tested or fully explored. This includes mixtures with Silkscreen Medium and Fabric Gel, GAC 900, Retarder, Gel Topcoats w/UVLS, Digital Grounds, and Acrylic Flow Release.

GENERAL INFORMATION

Do not mix with oils. For best adhesion, paint on clean, dry substrates that are free of oils and wax. Abrade non-absorbent surfaces for increased adhesion. Avoid freezing. Minimum film formation temperature is 49°F/9°C. Clean tools with soap and water.

GLOSSARY

Wet: The period when the paint retains the initial feel from the tube, before the loss of volatiles causes a noticeable change in viscosity and brush drag.

Workable: This phase overlaps the Wet period. The paint is becoming thicker, but not to the point of negatively impacting the painting process. It is within this range that many painters will find what they term their sweet spot.

Can Still be Reopened: This stage overlaps the Workable Range and allows for subsequent paint layers to be applied without disturbing the underlying paint, although it would still allow for the two to be blended and worked.

Touch Dry: Paint films are dry to the touch with no more than a slight surface tack. At this point it is much more difficult to re-open the paint film without considerable work, which can result in damage to the paint films.

Locked Down: Paint films should be water resistant and immovable. Also known as strap down. At this stage the film is stable and should remain in this state indefinitely.

ⁱLocked Down: Paint films should be water resistant and immovable. Also known as strap down. At this stage the film is stable and should remain in this state indefinitely.

ⁱⁱWet: The period when the paint retains the initial feel from the tube, before the loss of volatiles causes a noticeable change in viscosity and brush drag.

ⁱⁱⁱWorkable: This phase overlaps the Wet period. The paint is becoming thicker, but not to the point of negatively impacting the painting process. It is within this range that many painters will find what they term their sweet spot.

^ivCan Still Be Reopened: This stage overlaps the Workable Range and allows for subsequent paint layers to be applied without disturbing the underlying paint, although it would still allow for the two to be blended and worked.

^vTouch Dry: Paint films are dry to the touch with no more than a slight surface tack. At this point it is much more difficult to re-open the paint film without considerable work, which can result in damage to the paint films.

Disclaimer

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.