I thought I'd share this informative post regarding phalaenopsis "division" or in this case, an attempt to save a deteriorating plant.
The following orchid (see pic) is almost 20 years old and before division, spanned about 20" across and a foot high. It was a nice specimen plant often blooming on 5 spikes at once. However, being potted "forever" in the same pot, last summer, I noticed most of the plant leaves becoming limp and "shriveled" or "veined" due to drying out so I knew the roots must be bad (and they were).
Here is what I did to save the plant and produce more clones:
1-I carefully took the plant out of the pot and trimmed all dead/dying roots.
2-With sharp sterilized cutters (using a flame or bleach), I cut the orchid in about 2 equal parts. I really wanted to save the top so I kept as many live roots on the top half as possible when determining where to cut.
3-I dusted with ground cinnamon all open wounds, and re-potted both halves into fresh damp New Zealand sphagnum moss, making sure there is adequate draining (foam packing peanuts).
4-misted the plant on occasions when the moss would start to dry out and left in a warm, brightly lit spot.
It has now been almost 4 months since and you can clearly see new healthy leaves and roots on the top half of the plant (left) as well as 2 keikis (circled in red) on the bottom cut half (right). The bottom half will eventually die off but may end up producing more keikis before doing so. One is a basal keiki coming directly from the cut half and the other is a spike keiki from a healthy dormant spike that happened to originate on the lower half.
So that's it! I'm happy I acted before the plant was too far gone...now I have 3 plants and if all goes well, I will keep them potted together to form a nice specimen clump.
I hope this helps!