ABJD are made by casting resin into silicone or metal molds. Often, these molds are made of multiple pieces in order to avoid damage when the cast pieces are removed from the mold. Any place where mold pieces meet may create thin raised or depressed lines in the surface of the pieces called seams. Seams are created when resin seeps into the small crevices between mold pieces and cures. More prominent seams occur when the mold pieces are not carefully aligned.
Seams may be removed by cutting and/or sanding them smooth. BJD are made of resin, which is potentially toxic. It is unhealthy to inhale the dust as it doesn't biodegrade in the body and in most cases, causes crystallization or silicosis in the lungs after prolonged exposure. As with any sanding procedures, proper safety gear and ventilation are highly recommended.
Most companies do not include seam sanding in the price of the doll. Some offer sanding services for a separate fee. This is because it takes more time and work to give the doll a sanded finish. Prices for the service depend on both the company and the size of the doll, or in some cases, whether the doll has special parts or resin color. Only a few doll companies include the service with their standard dolls, but some may include them with their sales of limited edition dolls. Also, most companies do sell supplies to sand dolls, but in general anyone can go to their nearest craft or hardware store and get the same things.
Some resins cannot be sanded. Tanned or fantasy color skin tones are not usually suitable for sanding as it may cause discolorations. Depending on the resin type and color, it is possible to have minimum discoloration when sanding. Using or working towards a more finer grade of sandpaper can minimize differences in the seam and the general skin color. It is possible, even with "normal" or "white" skin tones, that a difference in color may be seen in the sanded area from some angles and in certain light conditions. The newly-sanded resin will usually oxidize in time, making the difference less noticeable. Sometimes a marbling effect can be seen after sanding some skin tones; this effect results when the pigment was not perfectly mixed with the resin before casting, or when the resin mixture separates slightly during casting.
Methods of Removing Seams
Normally, cutting by itself does not produce the smooth and blended surface that most are looking for when removing seams, but sometimes cutting seams is necessary when the seam is thick or sharp, in order to reduce the time it takes to sand down the seam. Cutting tools normally used are x-acto/exacto knives, ceramic knives, or even "cardboard" cutters. Aside from ceramic knives, many other "knives" have a potential safety hazard and the potential to damage the resin too much. The best recommendation is a ceramic knife as the blade is both blunt (will not cut you) and yet can cut through resin fairly easily and smoothly without cutting huge chunks at a time (allowing easier customizing). Currently many doll companies are starting to include the ceramic knives as part of their supply of tools for customizing. VolksUSA and eLuts are examples of companies that currently carry such knives.
There are two main types of sanding, "wet" and "dry". Both suggest using small, circular strokes and some may suggest a small figure eight motion. It's usually suggested to start with a lower grit of sandpaper and build up to a finer grit of sandpaper, depending on how strong the seam is. A general range around 300-1200 grits are common.
Wet sanding is usually suggested, if possible, because when wet sanding is done properly, the dust particles will not fly or float in the air to be inhaled. Therefore wet sanding is considered the one of the safest methods, though safety procedures are still an important precaution. Wet sanding usually involves either submerging the doll part in a basin of water while sanding, or constantly wetting the doll part and sanding tool while working over a bowl of water that will catch the resin debris. In the wet method, it is important to use the proper type of sanding material, as ordinary sandpapers disintegrate in water. Sanding sponges are normally used; other possibilities are wet/dry sandpaper and wet/dry sanding pads. Since water is involved, electrical devices are not advised because of the risk of electrocution. Gloves are suggested to protect hands.
Dry sanding requires proper use of safety gear (such as a respirator or heavy-duty mask and protective eyewear). Gloves are also suggested, especially if one has a sensitivity or allergy to the resin. The safest way to sand the dolls using the dry method is to have either a special sanding booth to contain, filter, and/or ventilate dust OR have a high-quality ventilation mask/eyewear and an open area with good air circulation. Even when sanding the seams using the dry method, it is advisable to work over a bowl of water to catch most of the resin dust and debris. Again, do not use electrical devices when working with water. Dremel tools are also usable for seam removal, but are normally for heavy seams and not for finer finishes because it can be difficult to control how much is sanded off.
Note that as with any form of allergy or allergic reactions, it is possible for one to develop an allergy to resin even after working with it for a few years.
- Sandpaper - A general range around 300-1200 grit is good, but can be more or less. This is usually the general all-purpose sanding tool.
- Sanding pad - Good for sturdier sanding and for flatter areas or sanding down heavier/sharp seams.
- Sanding sponges - Good for more contoured areas and can generally be used wet. Good for seams that are moderate to minimal.
- Sanding sticks - For sanding in harder to reach spots like inner corners, etc.
- Dremel - For speedy sanding of heavy/sharp seams. Usually recommended for reducing such seams before sanding by hand.
- Ceramic Knife - The most recommended knife to use as it's the safest, but still cuts through resin very well. (the blunt kind design for dolls, not the sharp kitchen knife)
- X-acto/Exacto Knife - Cuts through resin smoothly, but has a safety risk and can potentially cut too deep or damage resin.
- Ventilation Mask - To protect from resin dust. Most normal masks are not suggested as they don't filter resin dust enough, so it's recommended to have a mask that has a higher filtering rate or is made specific to such dusts.
- Gloves - To protect hands from the resin dust and avoid allergic reactions.
- Sanding Booth - Highly recommended addition to any sanding project, especially a sanding booth that has built-in ventilation.
- Towel - For general clean up or towel drying and laying out the resin parts to air-dry after wet sanding.
- Safety Glasses - Even if you wear glasses, safety glasses are suggested so that resin particles do not get into your eyes or damage your lenses.