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This week, more of the wisdom the teacher of my composting workshop passed on to new practitioners of the art.

Composting is 20 percent science and 80 percent art. The same directions followed by two different composters can lead one to success and the other to failure (in terms of speed of decomposition.) Variables such as the size of the pieces thrown into the pile, the available sunlight, the moisture levels, how often and how vigorously the pile is turned, how good the drainage is — all of these affect decomposition rates. The point is to start with a few basic rules and then make adjustments as needed.

Turning a compost pile is hard work and some backs just are not capable of it. Many books tell you to punch holes in a long piece of 2-inch PVC pipe and shove it down into the center of the heap to keep up necessary airflow. The problem with that method is that the pipe acts as a chimney, releasing into the air the heat you need for speedy decomposition. Instead, try this method: get four 2-foot lengths of PVC pipe and drill them full of holes. After your compost pile is about 2 feet tall, lay the two pipes on top, a foot or so apart, parallel to the ground. After you have piled on two more feet of compost materials, lay down the next two pieces of pipe. These two should also be parallel to the ground, but crossways to the first set of pipes. (If my directions are not clear enough, envision a tic-tac-toe grid with two feet of compost between the top two and bottom two lines.) The heat will stay in the pile, but necessary air will still get in because it will be drawn in from the sides.

Compost doesn’t have to be in direct sun, but it does need to be near a water source. However, you don’t want it in a soggy spot because bacteria won’t like it and the pile can turn anaerobic. (If the only spot you have left in your garden is a soggy area, you can put the compost up on recycled wood pallets or cement blocks.)

Do not use charcoal briquette remains in a compost heap. To make briquettes, the manufacturer takes wood and super-heats it to take out anything that might interfere with producing a nice even flame in your grill. As a result, the ashes of briquettes are super-concentrated carcinogens.

Shredded newspaper can be composted, as the ink is now soy based. While it won’t add nutrients, it will improve the texture of your soil. Glossy magazine pages, however, have lead-based print, so don’t compost those. Computer printer ink is not soy based, but according to the instructor, there is so little ink on the paper that it is fine to add some of it to your compost.

You can add wood shavings to compost, although they decompose slowly; the finer you have chipped the pieces, the better. However, do not add shavings of plywood (because of the glue) or composite woods (the formaldehyde used in some is a preservative. Think embalming fluid), or “exotic” woods because many have oils that are toxic.

You can add wood ashes (again, not from briquettes, plywood, composite wood or exotic woods) but they won’t absorb water well so don’t overdo it. They also are alkaline, so that is another reason to use an easy hand with them.

Do not add human waste to your compost heap. Every time I write about compost and make this statement, I get a rush of e-mails from earnest people giving me lists of all the countries that depend on “night soil” to grow crops. A quick perusal of the sorts of illnesses many of those poor souls suffer and die from should make you realize that it is a privilege not to be forced to make your garden double as your toilet. A home compost pile does not get hot enough to destroy all the bacteria in your waste, and you could end up contaminating your food.

Don’t add diseased plants or weeds about to go to seed. Some weeds are capable of continuing to grow for some time after being placed in the pile, and can drop their seeds there instead of in your garden. Many home compost heaps do not get hot enough to destroy all the weed seeds, so you can guess what happens when that compost is applied to your garden.

I was taught that successful composting required layering your carbon and nitrogen in precise quantities. That didn’t seem to work for me, even when I did have enough materials to build a pile all at once. So, within a year or two I stopped layering and simply mixed things together, but always with a slight feeling of guilt. It was a relief finally to hear someone say that layering actually slows down the decomposition. The important thing is not the layering, but the entire content of the compost pile, which I will cover next week.

Your pile will do better if you have a bottom layer of larger coarse pieces. While the teacher did not quote the Alaska Cooperative Extension’s bulletin on composting, she could have because that publication states, “Coarse materials are used in the first layer and should be approximately 6 inches deep for a good foundation. Tall weeds or old flower stalks can be used. Lay the foundation layer with some order over the full width of the intended pile. This will aid in a uniform breakdown and ease the repiling later.”

Next week: The rest of the teacher’s wisdom.