Week 4
Natural Materials
Natural has traditionally been used to mean materials derived directly from animal, vegetable, or mineral sources.
Both animal and vegetable materials typically break down or decompose in the elements. Decomposition may be altered by the way a raw material is processed into a final product. Animal and vegetable materials are usually harmless to the environment (in the raw state), and sustainable.
Mineral materials, such as stone and metal, are also called lithospheric materials because they originate in the lithosphere – the Earth’s crust. Mineral materials typically don’t decompose quicly like animal or vegetable materials, but many can be recycled or downcycled. Not all mineral materials are harmless to the environment; in fact, some are very damaging. Mineral materials are not typically sustainable.
It is preferable to use a material that has been minimally processed - as close to the original state of the material as possible.
Animal materials
- Leather
The highest quality layers of leather are colored using a translucent, pure aniline dye. This dye process renders beautiful color variation. Since this process is used on unfinished, top-quality leather, the finished product usually has a softer feel. Another coloring process, also used on top-grain hides, is a surface finish application called semi-aniline. This method produces a uniform color look. A third coloring procedure, called pigmented, coats the leather surface uniformly with an opaque color. This durable process covers most imperfections and is very commonly used. (Link to article)
Aniline is a coal-tar derivative, predominantly used as a chemical intermediate for the dye, agricultural, polymer, and rubber industries. It is also used as a solvent, and has been used as an antiknock compound for gasolines. It is classified as very toxic in humans. It is severely irritating to mucous membranes and affects the eyes, skin, and upper respiratory tract. (Link to article)
Organic dyes result in a firm but weak leather that is not a good choice for upholstery.
Links:- See the tanning process at Cudahy Tanning
- Leather Industry Glossary
- Reference Articles, Siegel of California
- Fur
The uses of fur in interiors is usually limited to upholstery trims and accessories, such as pillows and throws. There are several fur-bearing animals, including rabbit, lamb, lynx, fox and even nutria (which looks like a large rat). Sable and mink are the most expensive.
Links: - Wool & other animal fibers
Animal fibers are made of protein, and are usually easy to dye. Wool is used in fabrics and rugs. It is also a cushioning material in upholstered furniture.
Most other animal fibers have limited use in interiors.
Angora comes from the angora rabbit
Mohair comes from the angora goat
Cashmere (pashmina) comes from the cashmere goat
Alpaca comes from the alpaca, cousin of the llama
Links: - Silk
Silk is made from the cocoon of the silkworm, which eats only mulberry leaves. Production is labor-intensive.
Vegetable Materials
- Vegetable fibers are made of cellulose, which does not dye as easily as protein.
Usually used in fabrics for upholstery, window treatments, and occasionally wallpapers.- Cotton is the most important vegetable fiber today, mostly due to being the highest-yielding plant and having fibers that are easily separated from the plant.
- Flax fibers are difficult to separate from the plant. Flax is woven to make linen. The seeds of the plant yield linseed oil. Fibers are strong and soft.
- Jute fiber is collected from the stem skin of the jute plant. It is also called hessian. Fibers are strong, coarse. Burlap is jute cloth.
- Ramie plant is related to nettles. Fiber is harvested from the stem skin. Very strong, but not as durable as other fibers. Stiffness educes wrinkles when blended with cotton or other fiber. Fiber extraction is difficult.
- Hemp is related to the marijuana plant, but produces only tiny quantities of the THC found in marijuana. The plant is easy to grow, and fibers are high-quality, and have many uses. The seeds are even nutritious. Production of hemp is banned in the US.
- Coir is the coarse finer from the husk of a coconut. It is used for mats or rope, and is one of the only fibers resistant to damage from salt water.
- Sisal fibers come from the stiff leaves of the agave plant. Sisal is used for paper (lower grade) rope and twine (medium grade) and carpet (higher grade). Sisal is resistant to salt water.
- Bamboo
Bamboo is actually a really big grass. It is a very fast-growing plant, usually ready to harvest in 5-10 years. It is also very strong for its weight.
Bamboo can be used as a structural material or a finish material for floors and walls. Bambo fibers can be used in textiles.
Bamboo flooring comes in flat grain and edge grain – flat grain bamboo shows the “joints” in the natural material; edge grain bamboo strips are side-up and tend to hide these joints.
Links:- American Bamboo Society
- Building Green article: Bamboo Flooring
- PlyBoo bamboo plywood
- Cork
Cork is the bark of the cork oak tree that has been stripped off. This would kill most trees, but the cork regrows. The first harvest comes when the tree is 20-25 years old, and can be harvested every 9-12 years.
Cork is usually cut or ground up and made into sheets. It is usually used for flooring and wall panels.
Links: - Wood
Wood is divided into two groups: hardwoods and softwoods. The terms don’t really describe the hardness of the woods, as there are hard softwoods and soft hardwoods.
Softwoods are typically evergreen conifers, and include pine, fir, cypress, and spruce. Softwoods are usually used as structural materials.
Hardwoods are deciduous trees, such as maple, cherry, and oak. Hardwoods are usually used in furniture and woodwork.
Lumber sizes are given in quarters – 1” lumber is 4/4.
Dimension lumber has a nominal (2x4) and actual (1¾ x 3½) size.
A veneer is a very thin sheet of hardwood used to cover another material to look like solid wood. Veneers can be patterned and inlaid. Thicker veneers can be sanded and refinished.
Links:- A Guide to American Hardwood Species
- Characteristics and Availability of Commercially Important Woods
- American Hardwoods Rediscovered
- Decorative Veneer Cutting Methods from Flexible Materials
- Russin Lumber veneer information
- Hardwood Information Center - See these articles
- Engineered wood
Not strictly a natural material, engineered woods are materials made of wood and wood fibers. Engineered woods typically come in 4’ x 8’ sheets, and sometimes called sheet stock. Engineered woods contain glues and resins, which usually contain formaldehyde. Specify formaldehyde-free wood products.- Plywood – thin plies of wood glued together at 90° angles for strength. Can have stain-grade veneer on one or both sides.
- Chipboard – Wood chips glued together. Inexpensive, not as strong as plywood
- Particleboard – Like chipboard, but with much smaller chips. Often veneered with melamine for shelving.
- Fiberboard – Medium-density Fiberboard (MDF) is a popular material because it is smooth, inexpensive, and easy to work. It is made of small bits of wood (basically sawdust) that are bonded together with plastic resin.
- Masonite – wood fibers are steamed and stretched, then pressed and heated to form a board with a smooth finish. Some masonite is pressed into a mold to give a patterned finish.
- Straw
Wheat and rice straw is used to create strawboard; straw is compressed into a board, then faced with paper or other material and endcapped. The board is used instead of plywood, as a part of SIPs (structural insulated panels) for wall construction, as acoustic ceiling panels, and many other uses.
Make sure than any adhesives or added resins are safe and do not contain formaldehyde or produce VOCs.
Straw bales can be used to construct thick walls that are usually covered with stucco (the real thing, not EIFS). The bales are usually not structural; the building's structure is post and beam with the straw as infill.
Links:- Agriboard Industries
- Strawboard panels article from Toolbase
- Straw Bale Construction from Green Builder
- Linoleum
Linoleum is another product that is not natural in itself, but is made of natural materials. It is biodegradable, unlike most engineered woods (due to the glue or resin in them). It ia alsoantibacterial.
Linoleum is a mix of ground cork and linseed oil pressed onto a burlap or jute backing, usually used as a flooring material.
Artists use linoleum blocks to create linocut prints, similar to woodcuts.
Links:
Mineral materials
- Stone
There are three types of stone defined by the way they were created:- Igneous rock is formed from molten lava. If cooled slowly, crystals form in the rock, but if cooled quickly, they can’t. Granite is a slow-cooling igneous rock. Obsidian, or volcanic glass, is an igneous rock that cooled very quickly.
- Sedimentary rock is formed by sediments that are deposited, compacted, then bonded by silica or calcite in dissolved groundwater. Sedimentary rocks often have layers of different colors or include fossils. Limestone and sandstone are sedimentary rocks.
- Metamorphic rock is formed when other types of rock change over time due to heat, pressure, or other forces. The process of metamorphosis usually hardens the stone, as the mineral crystals in the rock fuse together and recrystallize. Metamorphic stones often show stripes or swirls caused by intense pressure. Marble is a metamorphic rock formed from limestone. Slate is a metamorphic rock formed form shale.
A stone’s hardness is rated on the Mohs scale, with talc being a 1 and diamond a 10. Marble is about a 3 on the scale, travertine a 4-5, and granite a 6-8.
Different types of stone can be used for flooring, countertops, tabletops, wall cladding, backsplashes, and shower enclosures. Harder stones should be used in areas that will have more traffic or wear.
Some stones are relatively easy to quarry and cut. It is heavy, so stone that must be shipped long distances will have high embodied energy.
Stone is porous and should usually be sealed.
Commonly used stones: Marble, granite, travertine, slate, soapstone, sandstone, limestone
Links:- Visual Stone Library from InfoTile
- Product Guide from Custom Stone Supply
- Granite Land Natural Stone
- Metals
Several metals are used in interiors, including stainless steel, copper, tin, aluminum, brass, and bronze. Although metals are typically used in appliances and fixtures, they can also be used on walls, floors, cabinets, and counters.
Metals have high embodied energy, but are usually recyclable. Mining often produces high environmental impact. Specify recycled metals.
Most metals will oxidize (rust) if not polished or sealed. Oxidization is beneficial with some metals.
- Gypsum
A common sedimentary mineral used to make wallboard, plaster, and cement.
Gypsum plaster (plaster of paris) is made by heating gypsum to 150 degrees and grinding it to a powder. It can be recycled by reheating and regrinding.
Glass-reinforced gypsum (GRG, GFRG) is used for interior decorative detailing, such as mouldings, medallions, columns, and ceiling tiles. Like plaster, it is usually painted.
Plaster can be made of either gypsum or lime. It can be molded into shapes or troweled on a flat surface. It is usually painted.
- Lime
Lime is made by heating limestone. It is ground and mixed with water to make lime plaster. It basically turns back into limestone as it dries. True frescoes are made of lime plaster.
Lime wash is similar to paint, but absorbs into a plaster or stucco surface like a stain. It develops a patina over time.
Lime is very caustic and should be handled carefully.
- Asbestos
A few minerals naturally form flexible fibers that are extremely heat resistant. The use of asbestos is highly regulated due to adverse health effects from exposure, even though only one type of asbestos is actually harmful.
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