I just got a used drysuit that seems to fit me better than I could've expected. I don't have thermals so just tried it on in shorts and a shirt and it felt decently roomy (until I started sweating and it got stuck to me). Down to the questions:
The neck seal was so tight I couldn't get it over my head without feeling like I was going to rip it by stretching it with my fingers. Is there anything special about trimming a neck seal? How tight should it be above land? Tight enough to only push one fingertip through? Loose enough to fit multiple fingers and pull it from my neck, if needed?
Since it is used, it's a bit dusty and the zippers were a bit stuck. Is there a particular lubricant or oil I should use?
First, carefully evaluate your neck seal. With the suit on a table or other convenient place gently stretch the neck seal and evaluate the condition of the latex. Is cracked, scaley, gummy, sticky, punctured, torn? Any of these indicates your neck seal is nearing or past its end of life and you should consider replacing. Is the latex stiff or supple? If stiff, consider replacing.
If the latex is smooth and supple, without nicks in the edge and stretches and relaxes well then next is to evaluate fit.
The neck seal does not need to be overly snug to do its job. In fact, too snug puts pressure on the blood vessels in the neck and in addition to discomfort can cause a diver to get light headed or even pass out.
The rule of thumb for drysuit seals is comfortably snug.
Before putting the suit on, take an old dress sock and dump some talcum powder in it and knot it above the mass of powder. Store this is a ziplock bag. Use the sock to dust talk onto the inside and outside of the neck seal (and the wrist seals). This helps preserve the seals and helps your head and hands slide through when donning. Re-talk after a dive when you stow your suit so it is ready for the next time you use it.
When donning your suit and passing your head through the neck seal put the four fingers from each hand through the opening of the seal and gently pry to the sides and let your head slide/squeeze through as if the neck seal is giving birth to your head. Let the seal slide over your face and down your neck assisting it gently with your fingers.....avoid stretching it to pass it over your face without touching your face. Slide the seal down so that it lays flat and comfortable around your neck. If the edge rolls make it so it rolls outwards not inwards....sliding/pushing the seal further down the neck can often keep it from rolling, and a new seal has more of tendency to roll than one that has been used for awhile.
If the seal is uncomfortably tight there are 2 options, you can stretch it or it can be trimmedc.
To stretch a neck seal, take a 3 liter plastic soda bottle and slide it halfway through the neck seal and let it sit for a couple of days, If you can't get a 3 liter bottle then some have had success with using a sauce pot, just be careful to not over-strech and tear the seal when putting it over the pot.
For trimming the seal, be warned that any nicks or unevenness in the cut can cause a stress riser and cause the seal to tear when stretched. Be absolutely sure you need/want to trim it before doing so and cut small increments such as 1/8 inch at a time, a little goes a long way. My preference is to take two 1/2" x 1" pieces of wood and clamp the seal tightly in between them leaving the amount I want to trim off exposed. I then use a very sharp scissor sliding against the wood as straight edge guide to smoothly trim the seal with as few cuts as possible. If there are molded ring guide lines in the seal, be sure to trim between these lines and not through a line if possilbe. Trim a 1/8th inch and then test the fit. Realize that with time the seal will stretch and relax so don't shoot for perfection, shoot for "good enough" or you may find that you have trimmed too much and need to replace the seal.
Alternatively you can just freehand cut with a sharp scissor or with the the seal stretch on a bottle or sauce pot your can use a fresh blade in a razor knife (utility knife) to cut a ring of the latex off....be careful with either method. With the scissor keep your cuts (closing the scissor) to a minimum and be sure to cut as straight and even as possilbe. With the razor knife, make sure the seal is not stretched too tight and be sure you keep the blade parallel with the edge of the seal....if the blade does not remain parallel it could cause a stress riser and the seal could tear/split.
As I mentioned, be sure you absolutely need to trim the seal before doing so.
If/when replacing the seal, know that they come in different sizes and shapes. You can usually test fit in a shop before buying or having it installed. Again the fit should be "good enough" as it will stretch and relax to a more perfect fit with use.
To care for your seal, keep it out of direct sunlight when not in use. Keep it away from chemicals (some sunblock lotions) and ozone/ozone producing substances/objects. Talc the seals before stowing, this helps slow the natural breakdown process of latex. If storing for long periods, put plastic bottles in the neck and wrist seals to help keep their shape and keep them from sticking to themselves. I also recommend spraying the seals with 303 Aerospace protectant a couple of times a season. It helps preserve the latex and protects it against UV and ozone...I have used this to very good affect on the latex seals of my whitewater kayaking drywear. Spray it on and massage it around with your hands, then leave it to dry or blot the excess.
For zipper care, an old tooth brush and Mcnett's Zip Care product works well. If dry and crusty, gently clean the zipper with the tooth brush...warm water and dish soap may help if you don't have Zip Care. Gently work the zipper pull back and forth in small sections. Lubricate the zipper with either Zip Care, Zip Tech, or zipper wax...a hard candle will work in a pinch. Rub the wax/candle on the outside of the teeth to leave a wax film along the length of the zipper. Slowly and gently work the zipper slide back and forth in 2 inch increments. A drysuit zipper should move smoothly with a little bit of resistance but should not take a lot of force or be overly difficult to open/close. Lubricate the zipper before stowing after every couple of dive outings, after cleaning it, or whenever needed. Stow/store the drysuit with the zipper open.
-Z
