Silvering a 17.5" f/3.4: Turning silver into stardust

First, thanks to the folks who made the OSW guide (Howard, Mel, Et al.) Also, thanks to Bob4VM for providing what was essentially, the solution to a hazy outcome. 

I've recently silvered my 17.5" successfully, thanks to Bob4BVM's input which is also in my log. It is probably why silvering the 17.5" f/3.4 was the success it was, producing a nearly flawless coating. It was my first attempt on the 17.5" and the 3rd attempt overall. I used a Swayze 12.5" f/4 as a test piece. The first attempt on that mirror failed, in a severely hazy coat with uneven edge coating due to incomplete cleaning. The AG sprayers were used on the 1st attempt. I find the AG sprayers to produce a mist that is inconsistent and too course in parts of the stream. The 2nd attempt, with ecolab sprayers, went about sideaways as it could, with either one failing to spray during the silvering process because the fluid level was too low for the siphon tubes. The 2nd attempt, did however, produce an even coating with excellent 100% zone coverage, with no flaws. It was just hazy, that's all. So I decided to experiment. I was able to remove the haze with red rouge. It is very slightly hazy, but the coating would be acceptable for astronomical use. 

Coating the 17.5" for the first time, and 3rd time overall, produced a coating that was astonishing to me. The coating is nearly flawless, and has a warm hue that is quite pleasing to the eye. Zero haze too. It's about as perfect coating as I could have hoped for. It also validated my mirror making, as there are no scratches to be found anywhere on the optical surface. This tells me that the processes I use to make the mirror work, and I can continue employing the processes I used to make more mirrors. In all honestly, by the time I coated the 17.5", I was tired as it was at the end of the day, and I already coated the 12.5 a couple times that day. While I was still meticulous with the cleaning stage, I did kind of just go through the motions during the sensitizing and silvering stages. I really did not think much of the coating during the silvering stage because I was so skeptical and worn down from the day. When the silver coat fully developed, I saw that there was no haze, I wasn't particularly moved and was nonchalant, so I went on to the MIDAS stage. Once I rinsed that off, and blow dried with cool air from the blow dryer, I was blown away and astonished that I was actually successful. This is the best coating I've looked at with my eyes. 

The silvering log is quite detailed, and can be a bit much for anyone to look at, with the very wide tables optimized for wide screen monitors. Important to me though, was engaging in the metacognition process, which I learned in university. This helps me analyze my own processes, what works, what doesn't work, and what I should change and why I'm making that change. It also keeps the entire silvering process on a linear track without improvisation that leads to random results or backward results that cannot be predicted. If I do change something, the reason for it is noted and easily tracked. I hope the section in the log showing the picture results of red rouge cleaning to remove haze is of benefit to some here. A hazy coat CAN be fixed. I've shown that. 

I''ve posted 14 pictures of the 17.5" mirror, it is in the table for the 17.5" under the "Picture result" column. I did two things different on the 17.5": 1. I used Chapin 1002 sprayers from the local Bi-Mart. 2. I rotated the mirror between silver burst episodes to produce as even a coat as possible. 

Here is a picture of the 17.5". I'm very very happy with this result. Flawless. Perfect. Can't wait to first light this mirror, although for the mirror maker, "first light" is a bit of a misnomer. I've had multiple nights with the 17.5" with the bare glass, during the parabolization process. Just not with the coating yet. 

Retrospective on Silvering the 17.5” f/3.4

List the good, the bad as lessons to learn for the next silvering process

The good:

• Practicing just the cleaning step with PCC over and over. 

• Fixed the haze on the 12.5” on the 2nd attempt with two passes of red rouge

• Rinsing the mirror with distilled water BEFORE cleaning helps see what dry/dirty spots look like when the water runs off. I recommend novices do this so they have a point of comparison when they do clean with PCC. 

• Coating can be successful when temps are in the high 70s (F) and humidity is in the high 40s 

• Sensitizing spray works fine in the ecolab sprayer. 

• Chapin 1002 48-Oz sprayers produced the successful coating on the 17.5”. Not the AG sprayers

• The first coating attempt on the 12.5” was educational- really taught me to clean that 100% zone. Harder to get the edge clean than the center. 

• Edge became less of a problem from the 2nd attempt on. 

The bad:

• Time consuming to practice the cleaning cycles. 

• AG Sprayers don’t really produce the fine mist needed for the agents to react before hitting the mirror surface.

• Edge wasn’t cleaned on the 1st attempt with the 12.5”

• EcoLab hand sprayers cannot function with 8oz or less in them.

• AG Sprayers don’t spray evenly nor do they spray fine enough. 

• The edge is not 100% perfect in the 17.5” but it is very nearly so. Just a 2” long strip on the 100% zone has slight discoloration. It is inconsequential.