During a recent dive trip the conversation on the boat turned to fog and masks. There were a few divers onboard that had not been versed in some of the tricks and suffered through a dive of flooding and clearing their masks trying to keep them fog free.
The general consensus is that 'contaminants' lead to more mask fogging. I thought I'd put a couple of the tips that I have found most helpful here for fog-free dives. Since I use (and love) a TUSA Visualator I contacted them to see if they had any advice on the subject. They were kind enough to respond and I have included some of their comments and advice below.
Clean a New Mask with Toothpaste
If you search on the interwebs you will find that this is a very common piece of advice. There is the opinion that there is a 'film' or 'separation agent' on the glass when it is new that makes it more prone to fogging. The nice people at TUSA* confirmed that this is indeed the case and "during the production process silicone film can form on the glass lenses which can cause increased fogging when new". They also confirmed that the best way to prepare a new mask is cleaning it off with a mildly abrasive toothpaste (think white stuff not gel toothpaste or something very gentle like SoftScrub). There are a few mask models out there that are shipped with anti-fog pre-applied. If you have one of those it is probably best to not scrub it off.
50 / 50 Water and Baby Shampoo is Amazing
For pre-dive cleaning, many rely on expensive anti-fogging agents or take the complete opposite approach and use 'spit'. I have found that a quick scrub and rinse with simple baby shampoo mixture works better than either of these methods. And, as for spit, it makes bacteria and other nasties more likely in the hard to reach cracks and crevices of your mask. This starts a negative cycle trying to keep the mask clean and free from contaminants.
TUSA confirms this opinion and says, "...over time oils and contaminants can build up on the lenses causing a layer on top of the lens that will increase fogging". They agree that "mild liquid soap or detergent" will be helpful in removing these contaminants and helping to provide a clean surface for for professional anti-fog solutions (which they recommend) to adhere to. They also agree that "Spit, although widely used, does not act as an appropriate anti-fog".
In my personal experience, cleaning my mask this way before every dive has been all that is required to keep it fog free. I have not found it necessary to use any professional anti-fog solutions.
Buy yourself a travel sized bottle and combine about half water and half baby shampoo. Squirt this miracle mixture in your mask and clean it with your finger and rinse prior to every dive. It has the benefit that any residue will not irritate your eyes (and it smells nice).
Check Your Breathing
If you try these methods and your mask is still fogging, try a friend's mask that has not been troublesome. If the previously fog free mask has a problem when you are using it...stop breathing out from your nose when you exhale. This is a more common problem than you might think.
These two tips have worked very well for me and provided me with a lot of crystal clear dives. I hope it works just as well for you.
*they point out that their comments are only recommendations based on dive and product experience, it is only meant as reference material. It does not supersede or alter their standard product warnings and warranties.