Joss - Good topic. You might want to contact a moderator and see about making your thread a 'sticky' so it will always be on top. Then people can easily find it.
In addition to what's been mentioned so far I've found the following items useful:
1. Storage - wine bottle corks or similar for protecting tips of fixed blades.
- clean thin white terry cloth hand/shop towels and rubber bands with which to wrap knives for storage after they've been cleaned, oiled etc. (Don't use these to wipe blades as they easily trap dust, dirt and grit - see below).
- zipper pouches big enough to hold the wrapped blade AND its sheath (I don't usually wrap the sheath unless it features a lot of silver work). I like to keep them together in a zipper pouch but I never store the knife in its sheath.
- standing floor safe - they're not that expensive, available anywhere guns are sold. It should reside in the basement if possible as thieves will not usually venture into a part of the house where they could be surprised and trapped. I keep a container of water in my safe at all times (humidity is very low in Denver). Really valuable stuff stays in a safety deposit box at the bank. Everything is insured.
Protecting blades and handles - after cleaning blades I apply a very light coating of "MILTEC weapons & machine shop grade synthetic metal contitioner" then wrap the blade as mentioned above. This stuff is great for lubricating folders and general rust prevention. I treat damascus and carbon steel blades basically the same.
- I routinely rub colorless, tasteless, odorless mineral oil on all ivory, bone, horn and antler handles. Sometimes I have to "re-hydrate" organic handles because they definitely shrink out here in Colorado, especially during winter. I do this by placing them on a plastic grate that sits on top of a container with 5 or so gallons of water in it. I rest a plexiglass box on top of the grate so that air can circulate. Moisture does not build up and condense (impossible out here anyway) because the grate and box are larger than the container. Several days of that works wonders. Then, instead of mineral oil, I'll apply a wax coating and rub it in good. My favorite is "BUTCHER'S bowling alley wax." It is a clear paste wax containing carnauba and other quality waxes rendered soft by turpentine and mineral spirits. Use in a ventillated area! I love the smell (in small doses) but what I like best is that it polishes to a hard finish giving the handle a very nice satin look while also retaining the moisture that the handle material just absorbed. In this way I can avoid the rather rapid dehydration of organic handle materials that causes cracking. Out here where we routinely see relative humidity hover around 12-14% I've learned 'the hard way' to be aggressive about protecting handles. Butcher's wax works great on leather sheaths too. (Test a small inconspicuous area first to check for unwanted discoloration.) Buff with a soft brush just like you would a good pair of leather shoes. I will also sometimes use RENAISSANCE micro-crystalline wax/polish for blades and handles, especially MOP (white, yellow, black lip etc. - see exceptions below). For something really cool though, contact Kevin and/or Heather Harvey, both ABS Mastersmiths in Belfast, South Africa about their special MUSEUM WAX. They make it themselves. It smells a lot better than Renaissance wax (which it resembles) and works on horses hooves too! Why not patronize the maker instead of some store?
Cleaning - I've also learned to keep lots of micro-fibre cloths around, rotating them through the wash so I continually have clean ones with which to wipe knives after handling. I also use these to apply wax and lubricant. They need replacing (not just washing) after several cycles of use.
- For guards/buttcaps etc. (silver, brass or whatever) that actually need cleaning (as opposed to simply dry-wiping) I use either Simichrome Polish or Haggerty 100 applied sparingly then polished with a microfibre cloth.
- 0000 or even 000000 steel wool is great for certain jobs, like bringing back the original shine of metal or hard plastic spacers (for example, stacked leather handles). Be gentle (but it's pretty hard to do damage because as steel wools go it's very fine).
Exceptions - I already inferred that MOP or "pearl" handles, escutcions etc. get treated differently (Renaissance or Museum wax only). The real 'buggaboo" are the various "blued" finishes. These can be a real problem depending upon how they were done. I consider all blued parts 'fragile' as far as finish goes. I don't put anything on a blued finish - just occasionally softly dry-wipe it with a microfibre cloth.
Everything I've mentioned is something that has been suggested to me by makers or museum people over the years. I learned the limits of these techniques/products (and the consequenses of not using them) by crossing the line here and there - either actively doing damage or finding damage that resulted from 'not doing.' Our family has discovered that we get a lot more pleasure from our collection by routinely handling many of the knives, not just looking at them. My wife and I rotate knives out of the safe and onto our desks for a month or two at a time where they see a lot of light use. You gotta open the mail with something, right? Since I'm constantly photographing knives from our collection, they get handled a lot that way too.
Collecting handmade cutlery is a fun hobby for me in part because it is a "hands on" hobby. We have a few knives that might be called 'investments.' As part of our 'retirement plan' so to speak, they are protected from handling and only come home from the bank safety deposit box once or twice a year for inspection and maintenance. All the rest is just part of our daily lives. Yeah, sometimes "stuff happens" but it's rare. When there is an accident and something gets a little ding on it we don't get too bent out of shape over it. We've lived long enough now to have experienced 'real' life problems and so I'm a lot more relaxed about our knife collection than I used to be. There was a time though... when I had to be told by someone more experienced than me to relax about this knife collecting stuff or it would eventually kill all interest and pleasure associated with knife collecting. It was further pointed out to me that (and this really got my attention) if that happened, I'd wind up getting rid of it all in a 'fire sale' just to get the monkey off my back. Then I'd be left with nothing but a bad feeling and crushing guilt over having 'wasted' so much time, energy and money. Wish I could've been smart enough to figure that out on my own, but I wasn't. This, IMHO, is why newer collectors (I include myself) should seek out experienced collectors for advice and friendship. People in their 70s and 80s who've been collecting for decades have so much to share. Plus, it reawakens their own passion for the hobby when some young lion collector comes along and shows an interest.