Hey guys
Two weeks ago
my delivery has arrived. It's a hand forged mech mod from Austria but it feels like my med doesn't hit anymore like in the beginning, since the silver plate of the copper bottom pin is off because i sanded it completely off because of arcing marks. All contacts and threads are clean. Results are a weak hit and my coils (dual, Ni90 round wire 0.09 ohm per inch - wotofo competition wire. run my rda with 6 windings about 0.11 ohm) ramp up a bit slower than before. I'm really helpless. 
You will always get a spark (arcing) on switch contacts when you hit it to take a drag. As you found out this marks the contact surfaces of both the switch and the battery. That is normal, there is nothing you can do about it. The lower resistance your build is, the more amps it draws, the hotter the spark will be, and the faster it will mark the contact surfaces.
You do not need to clean away the marks until they cause a noticeable increase in resistance. Eventually you will notice the hit becomes weaker and the switch will heat up, but that takes a while. I believe you have only had the mod for a couple of weeks, in which case you should not have noticed any reduction in performance due to this yet. I ran mechanical mods for years and probably only sanded the contacts every 3 - 4 months. I used 1000 grit paper and did it only enough (very gently) to take off the surface of the buildup, always trying not to take off any of the silver itself. Once you get past the silver coating and reach bare copper you'll find you will need to clean that surface more often. Copper is a very good conductor, so you should not notice any reduction in hit compared to with the silver coating. Silver is used only to avoid oxidation like you will get with copper. I have used grease like
ox-guard on my contacts (just a thin film is needed) which should reduce the effects from arcing, but that causes issues too and eventually I stopped doing that and just cleaned my contact surfaces more often. An agressive wipe with alcohol every 2 - 3 weeks is a good thing.
In my opinion any reduction in hit you have now is due to a degraded contact (increased resistance) somewhere in the mod or the atomizer. If I were in your situation I would contact the mod maker if possible and ask them about it. They can give you advice about the mod, and may also sell you a replacement switch contact so you will have silver on it again, just don't sand it off again
. Batteries that are rated for the amp draw you are pulling are important too, as is buying them from a reputable vendor you trust to sell you authentic batts. With a 0.1 ohm build in your setup you are really stressing them and if they are actually only rated say 15 - 20 amps they may well degrade quickly. They will also be a safety issue.
Vape safe and the best of luck with the mod!
