How To Make A Professional Soil Monolith Model
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Soil Monolith Procedures 21-23
21.) As the frame is raised about 3/4", quarter-round molding can be placed (tacked lightly) along both sides and ends to hold profile intact until glue has dried. This step may or may not be needed depending on texture, soil moisture content, and disposition of the monolith. Ideally, if molding is used, it should be loosened before glue completely hardens although it can be removed later or allowed to remain.
(Monoliths can be transported at this time if care is exercised in keeping them flat and relatively free from drastic bumps).
22.) Ideally, the exposed profile is picked or dressed to show desired structure or finish before the soil dries; however, it can be remoistened for this process. (Dentists' picks, walnut picks, or other fine tools are used for this process . Avoid tool smear marks on finished surface - they will be very obvious on the finished monolith).
Pick the profile, allowing about 1-1 1/2 inches of soil to remain. Remove all loose soil particles from the dressing process with low air pressure.
23.) Allow soil monolith to air dry for 2-3 weeks - it is absolutely essential that all moisture be removed from the monolith before applying "hardening compound", otherwise very undesirable and almost irreversible chemical reactions occur.
HARDENING COMPOUND PREPARATION AND FINAL SOIL MONOLITH PROCEDURES
- Prepare hardening compound at least 24 hours in advance of pouring the monolith (consists of mixing 1 pint acetone- high strength- with 37 grams vinyl chloride/vinyl acetate resin {Union Carbide, Corp.}. This VC powder should dissolve completely - it may take 2-3 days to dissolve.
- In a well-ventilated area, pour the hardening compound over the soil, completely saturating the surface, and taking care not to "pond" more liquid in structural cavaties than can readily be absorbed. Due to textural differences and absorption rates, the amount to pour and elapsed time between pours varies considerably.
- The objective is to completely saturate the soil profile. Usually on fine-loamy soils, pour 2-3 times and use about 1-1 1/2 quarts of hardening compound per monolith. On some occasions, a second pour is done within one hour of the initial, followed by a third pour 24 hours later.
- Allow profile to dry for about one week. Remove excess glue, which usually requires sanding.
- Paint or finish mounting board as desired and apply soil name plaque and/or lettering, horizonation, depth, etc. (A flat, black background is best for emphasizing the soil profile).
Note: While there may be simpler, easier methods of extracting soil profiles and procedures requiring less time for preparing soil monoliths than this process, this process results in a better end product. Total time is estimated at 20-40 hours per each monolith.
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Permission to digitize and display the images and text of "How to Make a Soil Monolith" was granted by Dr. Maxine Levin, USDA's Agricultural Research Service.