1. Writing on a whiteboard
Bold color dry erase markers leave no residue, or 'ghosting'. Low odor markers, depending on the color, are known to leave marks that are difficult to deal with.
Dark cloth bath towels can be cut to convenient sizes and used as inexpensive erasers.Advantages:
Low cost when compared to commercial erasers
Less marker lint is left behind than commercial erasers, which need to be vacuumed to get rid of this lint.
Cloth can be washed.
To prevent anyone from removing these towels, tie some fishing line through a hole in the cloth and loop the other end around a thumb tack.
To make a hole in the cloth, fold a corner of the towel down about 3cm. Twist the folded area to a tip or point, and use scissors to cut a tiny square. When unfolded, this will result in a small hole towards the edge of the towel, but with enough fabric remaining that the hole is secure.
3. Making your own whiteboards:
Melamine coated PCB, also known as shower boards, is the same material used for commercial, non-magnetic whiteboards. It is available in 4' by 8' sheets at most home improvement stores for around $13 per board.
3.1 Free method:
The hardware store may agree to cut the shower boards into whatever sizes you need, if you let them know "it's for the children!" ;)
3.2 Inexpensive method:
To cut the shower board, mark a straight line on both sides to indicate where your cut will be. Use a meter stick and a dry erase marker to make these lines.
With a utility knife or box cutter, cut a tiny line into the board.
Use the meter stick as a cutting guide - you'll need someone to hold each end.
Repeat this 3-4 times.
Turn the board over, and do the same to the other side.
The board will now break relatively cleanly.
Use the utility knife to smooth out the edges.
3.3 Best results, most expensive:
On a table saw, use a fine-toothed, carbide Alternate Top Bevel (ATB), negative hook melamine saw blade, or triple-chip saw blades. ATBs will give a better cut, but triple-chip cutting edges are more durable when used against this abrasive material. These saw blades are $150 per blade, and will last for years and can be resharpened if it is only used to cut melamine. The ten inch blades usually have 80 teeth and are specifically designed to minimize chipping and tear out.
You can also use a range of less expensive blades and also use a router with a flat bit (good option) or a circular saw (ok).
1. Set the saw blade at about three quarters of the thickness of the board and make a pass with the board on the saw. This will cut most of the board.
2. Leave the blade in position and cut the board completely from the other side.
The top side of the board, with reference to your saw table, will be perfect, and the bottom side will have minor tearing.