Hmmm, interesting but I have to ask this, What do you use to hold the mirror in the optimal position where you can see the joint to deposit the weld and yet one can simultaneously can place it in a location where the face of the mirror will be less exposed to spatter??? This is how you want to position your mirror...
Many moons ago, before modular construction became all the rage in building nuclear powered submarines for the USN, there always seemed to be an ever increasing amount of mirror welding to be performed especially in the wet docks which was where the subs were parked in order to sign off as many joints for Navy acceptance which by the time the subs reached the wet docks, most of the welding with mirrors were to sign off pipe hangers and their repairs as well as some repairs of both, structural as well as pipe joints found in various locations throughout the subs compartments. This was part of the effort in order to prepare the subs for both Sea Trials and finally commissioning to the USN.
There were many occasions where we had to use multiple mirrors just to get a clear view of the repairs that needed to be completed in order to sign off the joints in question and we always used the magnet based mirror systems which had three joints where one could swivel one and adjust the next one, or the one closest to the Stainless steel sheet metal mirror holder which had sleeves designed into them so that we could slide in, or out mirrors whenever we wanted and very quickly. We would set into position one mirror to amke clear a corner which we couldn't reach and look into initially, then we would use another mirror to help us look at the joint inside that zone clearly which would then enable us to aim our 3/32" dia. electrodes to deposit maybe only a 1/2 of an inch of weld metal around the corner of a hanger that if not deposited and NDT'd, the Navy wouldn't accept it and we couldn't sign off on it as another item on the punch lists for the Navy to accept the vessel.
We also design a variety of extensions as well as some pretty nifty GTAW torch extensions as well to get into some pretty tough locations which were always found either in the engine rooms or in the torpedo rooms as well although on occasion, there were some doosies to be found in the reactor and COC compartments as well yet, they were more frequent in the first two compartments I mentioned initially... We tried the stainless polishing but we found it not to last anywhere near as long as the mirrors did for our applications because, the trick of using a mirror is to optimize the location of the mirror in relation to where one could estimate where the spatter might fall, and then if the use of naother mirror is required in order to fine tune you angle of sight, then naother mirror was used and by doing so, helped prolong the use of each mirror.
I've done way over a thousand mirror welds so I know what I'm talking about and as an employee of General Dynamics Electric Boat Division, we in the welding department have tried all sort of different scenarios and we came to the conclusion of what worked best for some of the tightest locations to get to by any seasoned shipyard welder from other shipyards all over the country came to experience as the toughest place to mirror weld - HANDS DOWN!!!
Even some of the NASA welders were sent to the EB welding school to get mirror welding training so, believe me when I say that I know what I'm talking about!!! I'm not bragging but, we were without a doubt amongst the best in the world with a mirror or two, or three, or more!!! :) :) :) I worked the third shift crew which performed this type of work all over the shipyard, and not on just one boat and we got more work done on that shift because there were less people crammed into the subs, so we didn't have the distractions found on 1st or second shifts.
So plan your placement according to what I previously mentioned and use more than one mirror if you need to because you can!!! Also, remember that you will see and make oyur moves as if you were welding without a mirror when two mirrors are used - CAPECHE??? Good Luck!!! Yeah right!!! I've broken so many that if it weren't for bad luck, I wouldn't have any luck at all LOL!!! :) :) :) :) :)
Respectfully,
Henry