Last blog we discussed why our color can drift when working with dyes and the importance of using my beloved storyboard to keep “shift” from happening. In this blog let’s focus on how even a simple wiping stain can have color changes.
First, what is a wiping stain? Wiping stains are transparent or semi-transparent coatings that color the wood and accentuate grain by creating definition and bringing out the woods natural character. Stains should be applied directly to the bare wood surface. Stains merely provide color; although I said coating in the previous sentence, stains do not provide a protective film. Wiping stains are constructed of pigment, solvent and binder/resins. The resins in them can, and will, be the reason for adverse effects on the performance of your sealers and topcoats if not applied correctly or with compatible finishes. Some finishers like to blend their own stains by just using colorants and a solvent. Although this will provide you with color to be wiped, you can have issues down the line with color bleed, fade, adhesion and wrinkles without a binder present.
Many finishers prefer using wiping stains for the ease of use and the ability to adjust the hue of color in the application process of wiping on or off. Some VERY important rules that you must remember when using a wiping stain, stir your stain frequently to maintain a consistent color, be sure to WIPE IT OFF and allow it to DRY properly. Here are some common reasons why we get “color shift” when using wiping stains.
Sanding—The type of sanding material and grit will affect both color and appearance. Sanding all substrates to the same grit will not always produce the same color. Solid wood should be sanded with a lower grit to open the profile, plywood sand one to two grits finer than the solid wood to even the colors, veneers sand one to two grits finer than the plywood to blend in with the other two substrates without getting too dark. i.e.; solid 120, plywood 150-180, veneer 220-240.
Dwell time—Allowing the stain to penetrate into the substrate for different time rates will affect the color. Wipe on/off will produce light color; longer dwell time will produce a darker color. Here in this photo, you can see the stain was wiped off at 10 seconds, 30 seconds, 1 minute and 2 minutes. The other difference in this picture (7) is that the same stain was applied on maple plywood, sanded the same on both boards but one plywood was MDF core the other plywood core.
Wiping technique—Wiping excess stain off with a clean rag vs. dirty saturated stain rag will give you consistent color and better adhesion. Type of rags, cotton, cotton blend or polyester will absorb and affect color left behind. Not fully wiping off your stain will lead to adhesion problems or color bleeding up into the clear coat which can cause a stain blush, or the stain will migrate itself out of the coating and become sticky a year or two down the road.
Conditioner—Wiping a clear base stain on the surface of the wood before the stain color will control some of the blotchiness that can occur in open grain or pores areas. Conditioners fill the open “thirsty pores” so the color stains penetrate more consistent as well as less than if not conditioned. When conditioning you must allow it to dry before applying the color stain to receive the effect and appearance you’re after. If conditioner is left too long before color stain is applied, the effects of the conditioner can be lost and color can shift. Be consistent in time frames. In this picture, the right side was conditioned before staining.
Time frame from sanding to staining can affect color appearance. Wood is always moving, moisture, humidity, temperature, what and how you sand today will not have the same profile tomorrow.
The temperature of the board will affect how the satin penetrates and dries. When the board is a warm temperature the stain applies evenly vs. cold temperatures causing an uneven blotchy effect. See Picture
Dry times will affect the color. Rushing the topcoat before the stain is dry will change the final color when it is cured. This picture shows what will happen if the application is altered. The board on the left was all steps applied and allowed to dry correctly. The middle board was cutting the dry times down. The far right board shows rushing the system, doing all three steps within 5-10 minutes of each other. Notice the last color where it was rushed also shows signs of color bleed and blushing of the sealer to topcoat
Pigment load—Stains have a binder that controls the pigment load excepted. When using a stain that is in excess of the pigment load or intermixing incompatible colorants or stains, inconsistency and adhesion will occur. Then real SHIFT HAPPENS. Here is a picture of what happens when we want to add a stain into our clear coat to shade.
Substrates—Staining solid wood, stain penetrates less. Plywood, stain penetrates deeper, reflects the appearance of the type of core underneath and can show slight blotchiness due to cut of veneer layup. Veneers will become saturated quickly so fine sanding is necessary to avoid dark blotchy stain areas. Even when using the same stain on different woods species your color will change. Remember the natural color of the wood will always influence the color of stain. This picture shows the same stain applied to Ash, Cherry, Oak, and Maple
Texture or grain will shift the color appearance
These are just a few ways our stain can shift in color. In my next blog, we will talk about other influences on color shift like clear coats, lighting and sheens. Happy Thanksgiving everyone.