When you plant a coin garden, you need to leave them buried a couple months or so... preferably over the winter or other wet weather. When a fresh coin goes into the ground, in most cases, the "matrix" of the ground mineralization will temporarily mask the coin. When it sits in the damp ground for a little while, it will develop a "halo" around it. A halo is basically an area of ground immediately surrounding the coin that begins to become saturated with metal ions that leach from the coin itself through the same basic process that electrolysis works on. I'm no scientist, but I believe I described this as accurately as possible. Anyway, the longer a coin is buried and, depending on the ground conditions, the larger the halo grows.... the more the total signal of the coin will "stand out" against the surrounding ground matrix. This principal works well for us in that really old coins will develop large halos that make them easier for the detector to locate, thus increasing the depth at which your machine will go.
For example, a 100 year old indian head penny sits in damp ground and develops a large halo around it.... this can be seen as a dark black or greenish area of ground around the coin.... You may be able to detect this coin from 10". The same penny buried for the same length of time, but in drier or sandier soil that prevents a pronounced development of a halo around it, may only be detected from about 5".
Another phenomenon is when you get a target with a large halo around it, the halo itself actually begins to be a significant portion of the target signal itself..... so much so you notice wierd things such as...... faint signals that disappear when you dig a few inches of dirt off the top..... coins that were not detectable in dry ground, suddenly becoming very detectable when the ground becomes damp..... even getting a faint signal from the clump of ground with the halo in it after removing the target.
Sorry to drag on here.... just hope I illustrated a little how a coin garden will work or, initially, not work. Good Luck and HH, Mike.
