The ABCs of Staining Castings - How-To #2 Booklet

Posted by Richard E. (Ben) Bendever on 6/12/2015 to Tips & Techniques

The ABCs of Staining Castings

Typically, there are three types of castings found in a kit: plaster, resin and metal. Since the manufacturing process of each of these castings is molding, all three casting types will have some sort of mold release that affects the staining/coloring process. Although the mold release used in plaster castings has been absorbed into the gypsum and cannot be removed, the mold release on resin and metal castings is best removed with vinegar and warm water. Only after the resin and metal castings have been cleaned and thoroughly dried, can the staining process begin.

Background

Gypsum - The plaster (Hydrocal®, LabStone a/k/a Dental Stone, etc.) castings that you receive from a manufacturer are not all created equal. They range from the weakest and least expensive (referred to as Plaster of Paris) to the strongest and most expensive (varying grades of Labstone—mostly used by Dentists and Orthodontists for impressions and dental repair). Typically, if the castings are white in color they may be weaker, which is why these castings are usually much thicker. The white gypsum casting is made thicker so that it will be less likely to break, especially under extreme conditions such as being knocked over on the workbench or being thrown around by delivery personnel. Castings made of a stronger material do not need to be as thick.

No matter what type of gypsum from which the casting is made, if some sort of sealing product is not applied to the casting, heat and humidity will cause the casting to deteriorate over time. This explains why older castings leave a residue when touched or handled. Additionally, no matter what type of mold release the manufacture uses (or does not use), in order to create a consistent finish, it is best to apply a sealant such as a couple of coats of Doctor Ben’s Aged Driftwood Weathering Stain (#1097) to the casting. This will stabilize the casting before beginning the staining (coloring) process.

Resin - As in gypsum castings, there are many different types of resins used in casting. Some resins are more stable than others, which means that these castings are less likely to warp or deform when subjected to heat and humidity and/or not maintained in a flat position. Because resin materials are so abrasive, mold release is used to assist the production in order to get more castings before the resin wears out the mold. Even after a thorough warm water and vinegar washing, an automotive primer may be helpful to aid the binding properties of the Doctor Ben’s Stains, as well as to stabilize the staining process.

Metal - Metal castings are typically spin-cast in vulcanized rubber, and a strong silicon mold release is used in order to speed the part release. When the white metal is in its liquid state, the temperature is near 400 degrees. After the casting has cooled, the mold release literally will have been cooked into the smallest crevasses of the metal casting. Even after a thorough warm water and vinegar washing and scrubbing with an old toothbrush, an automotive primer or etching primer may be helpful to enable stains to bond to the white metal or brass castings.

General Preparation

These instructions will recommend the Doctor Ben’s line of Weathering Stains, Solutions, and Industrial Pigments for sealing and finishing the gypsum castings. These steps are also applicable to resin and metal castings after the aforementioned steps are taken.

After the castings have had any unwanted flash removed from around the edges and openings, they are ready to be sealed. Using a medium size, soft brush, apply several light coats of Doctor Ben’s Aged Driftwood Weathering Stain (#1097) in multiple directions, waiting a few minutes between coats. Be sure to coat the backs and the rough edges of castings, because rough surfaces tend to be more porous than smooth, molded surfaces. When possible, allow the sealed castings to set overnight, even though they may seem dry after just a few moments.

Reinspect the castings for imperfections or voids that were not obvious when the castings were a stark white color with no contrast. Reseal any repaired spots and any areas that may have resisted a sealant due to a mold release product used by the manufacturer (gypsum, particularly). Allow this reapplication to dry before proceeding.

The following will address how to stain castings of specific architectural textures and shapes. These techniques may also be used for nonarchitectural castings such as automotive, machinery, rolling stock, and figures. The coloring and staining of nonarchitectural textures will be discussed in another article.

Brick - Bricks come in many shades of red, orange, brown, and even off-white. Select a base color that best fits your geographic location. For these instructions, Doctor Ben’s Pacific Redwood Weathering Stain (#1088) will be used as the base color. When working in miniature, a variety of brick colors looks much more realistic than using one standard color for all of the brick buildings in a scene or layout. Fortunately, Doctor Ben’s has many shades of red and brown stains from which to choose, as well as many shades of Industrial Weathering Pigments that, when mixed with water or alcohol, can be applied as a brick color.

Some modelers prefer to start with a single base color and then, for the next structure, mix in another stain color to change the base color just a bit. Then, for the next building, another color will be added to the cocktail, and so on. This technique can produce impressive results, but don’t get too carried away. A huge benefit of using this technique for a base color is that no two structures will ever be colored exactly the same.

Apply the base color by dry brushing the brick surfaces with a stiff, flat brush. It is best to always use the largest brush that you feel comfortable with for the job. A larger brush can hold more paint and will spread it farther and quicker than a smaller brush. Don’t worry if some of the brick color spills over into the mortar lines. In addition, don’t worry about perfectly even coverage; uneven coverage looks much more realistic in modeling miniature structures. Let the base color dry overnight.

Use a soft brush to apply the mortar color. Doctor Ben’s Worn Concrete Weathering Stain (#1095) will be used for this step. The instructions for the Doctor Ben’s Weathering Stains say to shake the products very well; however, when modeling mortar, hold off shaking the jar at all. Just dip the brush in the very top of the Worn Concrete stain, and, starting in one corner, allow the capillary action to pull the stain across the brick casting. Allow this small section to dry (a hair dryer or heat lamp will hurry the process along) to see if the mortar color is dark enough to suit. Should a darker mortar be needed, stir the Worn Concrete stain gently to bring some pigment to the top of the jar. If the mortar is too dark, dilute the stain by first dipping the brush in a little rubbing alcohol and then the stain. After the mortar stain shade is decided upon, use the same “capillary action” method to stain all of the mortar joints.

Should Worn Concrete stain end up on top of the brick color, lightly dampen a paper-towel-wrapped finger and wipe over the mortar stain needed to be removed. To remove the Worn Concrete stain, work quickly, but gently, in a small area at a time, changing out the area of the paper towel when necessary. This will remove most of the stain from the brick faces, while leaving the mortar color in the joints.

After the mortar staining process is completed, the last step is the random staining of individual bricks with different stain colors. This goes much faster than it sounds. Use at least two or three different colors, such as Doctor Ben’s Knotty Walnut Weathering Stain (#1087), Doctor Ben’s Black Mahogany Weathering Stain (#1086), and perhaps Doctor Ben’s Durty Black Weathering Stain (#1091) and Doctor Ben’s Rustic Barn Red Weathering Stain (#1089). Randomly stain only about 10% of the bricks in varying colors by just touching the very tip of the brush into the chosen stain color and then very lightly on the brick face. When enough of the varying colors have been applied for a natural look, allow the surface to dry completely. Next, turn the brick wall upside down and spritz the wall with a 50/50 mixture of Doctor Ben’s Instant Age Weathering Solution (#1152) and alcohol in a Doctor Ben’s Micro Blaster (#2925), and allow the wall to dry. If desired, lightly dust on Doctor Ben’s Weathering Pigments for a little more weathering. Finally, if the casting will be handled a great deal, lightly spray pump hairspray or a dullcoat on the wall section to seal and protect the finish.

Stone – The process of staining stonework is the opposite of the process of staining brick. To create a realistic look for stonework, start first with the varying stone-color stains and finish with the primary stone-color stain. The stains needed for this process are Doctor Ben’s Hardwood Maple Weathering Stain (#1083), Doctor Ben’s Black Mahogany Weathering Stain (#1086), Doctor Ben’s Knotty Walnut Weathering Stain (#1087), and Doctor Ben’s Worn Concrete Weathering Stain (#1095), and they will be used in that order. These stains are used initially in a very weak (barely shaken or stirred) state. This means that there is more liquid than pigment in each brush full.

The percentage of stones that are stained with brown shades will determine how gray or how brown the stonework will end up looking, so keep the desired effect in mind as the colors are applied. Start by giving the entire stonework area a coat of (full strength) Doctor Ben’s Aged Driftwood Weathering Stain (#1097). Follow this step immediately with the application of the additional stains; each one will cover progressively more stones than the previous stain. Apply the Hardwood Maple stain in a random pattern on about 10% of the stones, remembering to use a weak brush color. Next, apply the Black Mahogany stain, covering more stones than were covered with the Hardwood Maple. Do not be neat when applying the various stone colors—Mother Nature is not neat (overlapping some of the previous colors with the new colors is also acceptable and will give a more natural appearance).

Next, apply the Doctor Ben’s Knotty Walnut Weathering Stain (#1087). Again, a weak brush color is used, so don’t be afraid to add a light coat of the Knotty Walnut stain to some of the Hardwood Maple and Black Mahogany stones. Stain more of the stones with the Knotty Walnut stain than with the previous colors, and apply two and three coats to some of these stones. The additional coats of stain on some stones will result in some stones with medium brown colors and some with darker brown colors. (An option at this point is to select a color such as Doctor Ben’s Nautical Teak Weathering Stain (#1084) to be used as the rarest color, with only one or two stones arbitrarily stained.)

The next step is to apply the mortar color, Doctor Ben’s Worn Concrete Weathering Stain (#1095), using the “capillary action” method: Dip the tip of a brush into the Worn Concrete stain and dab it lightly on randomly selected areas of the mortar, allowing the capillary action to pull the stain onto the mortar. Repeat this step until all of the mortar is covered with the Worn Concrete stain. If there is concern over contaminating the Worn Concrete color when the used brush is dipped back into the jar, either wipe the brush first or pour a small amount of the Worn Concrete stain into a small container beforehand. If the Worn Concrete color ends up on top of some stones, leave it there. This will just add additional color variety. When satisfied with the staining process, turn the stone wall upside down, spritz the wall with a 50/50 mixture of Doctor Ben’s Instant Age Weathering Solution (#1152) and alcohol in a Doctor Ben’s Micro Blaster (#2925), and allow the wall to dry. If desired, lightly dust on Doctor Ben’s Weathering Pigments for a little more weathering. Finally, if the casting will be handled a great deal, lightly spray pump hairspray or a dullcoat on the wall section to seal and protect the finish.

Wood – The method of staining wood castings, whether trees, logs, piles of lumber, or structures, is not only dependent upon a predisposition for what it should look like, but also upon the geographic location of the wood. For instance, weathered wood on the East Coast of the United States tends to be in the shades of gray/green driftwood; wood in the Colorado Mountains ends up fading in shades of red and brown. So the best way for deciding the look of the wood is location, location, location.

Whether the resulting look is to be a light, sun-bleached color or a dark, rotted effect, begin with a wash of Doctor Ben’s Aged Driftwood Weathering Stain (#1097) on the whole casting. A note to remember—even sun-bleached wood is quite often rotten and dark on the bottom (or the part closest to the ground). Rain or water and dirt splashing up from the ground leave a wet residue, creating this look.

For wood structure castings, follow the Aged Driftwood Stain with multiple coats of the stain color(s) that the casting originally may have been when it was freshly painted. The wood may have been painted two different colors or even several colors; either way, work with a brush not much wider than the board width, building up color board by board, and omit some boards right from the start (leaving them gray).

For a little more weathering detail, brush on some “liquid masking” between coats to create the peeling-paint effect. Next, for variety and to pull out some of the detail, randomly apply thin applications of Doctor Ben’s Natural Pine Weathering Stain (#1082) to a few boards. For slightly darker boards, use Doctor Ben’s Rustic Oak Weathering Stain (#1081). Remember, apply thin applications at first. Build up tone and color board by board—slowly. Apply some full strength Doctor Ben’s Knotty Walnut Weathering Stain (#1087) into the wider cracks to bring out the detail (especially in the rotten areas and on the bottom of each board). When satisfied with the staining process, turn the wood structure upside down, spritz the structure with a 50/50 mixture of Doctor Ben’s Instant Age Weathering Solution (#1152) and alcohol in a Doctor Ben’s Micro Blaster (#2925), and allow the structure to dry.

Closing

The techniques described here are only guidelines to help you to create the look you want. The important thing is to do it the way you will like it. The methods outlined here will take a little practice. Just jump in and try and don’t be afraid to make a mistake or two. Mistakes are only opportunities. You’d be surprised how many “mistakes” actually work.

FYI The Practice Wall kit used to the illustrations for this booklet was modeled by Richard E. (Ben) Bendever and weathered using Doctor Ben's Weathering Stains, Solutions & Pigments as described in the kit instructions.

 

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