Home

Please support mflenses.com if you need any graphic related work order it from us, click on above banner to order!
SearchSearch MemberlistMemberlist RegisterRegister ProfileProfile Log in to check your private messagesLog in to check your private messages Log inLog in

Haze glass
Post new topic   Reply to topic
Home   DIY
View previous topic :: View next topic  


PostPosted: Sun Jun 16, 2024 5:13 pm    Post subject: Haze glass Reply with quote
Did anyone tried acrylic polymer to treat the hazing of the glass?


PostPosted: Sun Jun 16, 2024 5:27 pm    Post subject: Reply with quote
How would that work? Sorry, I can't imagine how a clear coating would mitigate haze. Smile


PostPosted: Sun Jun 16, 2024 8:15 pm    Post subject: Reply with quote
On some lenses (poor condition ones for experimenting with) I have noticed that sometimes wiping a thin layer of oil over the surface significantly reduced the visibility of the haze.

At other times wiping them simply with distilled water reduced the haze for a little while, but then returned after a few days.

Acrylic polymer might work but I suspect the layer would be neither very thin nor even; it might affect IQ at larger apertures.

I think it depends on the nature and location of the haze but if the lens is of otherwise little value then you can experiment. The acrylic might just flake off when cured though.


PostPosted: Fri Jun 28, 2024 10:18 pm    Post subject: Reply with quote
in few projector lenses i have(angenieux, kipronar) i found haze , probably it has to do with the heat and cold these lenses were exposed to; the haze didn´t seem so much visible until i´ve opened the lens and clean it properly . Many times i questioned myself if cleaning might have provoked the haze to appear, as before cleaning the haze had a different shape. Most of the times i would only use isopropyl , thanks to your information, i have found out there are lenses that have very fragile coatings (early minolta), but i guess , cleaning these lenses and removing the coatings on them , wouldn´t provoke any haze, isn´t it?


PostPosted: Sat Jun 29, 2024 10:15 am    Post subject: Reply with quote
kiddo wrote:
in few projector lenses i have(angenieux, kipronar) i found haze , probably it has to do with the heat and cold these lenses were exposed to; the haze didn´t seem so much visible until i´ve opened the lens and clean it properly . Many times i questioned myself if cleaning might have provoked the haze to appear, as before cleaning the haze had a different shape. Most of the times i would only use isopropyl , thanks to your information, i have found out there are lenses that have very fragile coatings (early minolta), but i guess , cleaning these lenses and removing the coatings on them , wouldn´t provoke any haze, isn´t it?


There have been a couple of Minoltas where the soft green coating had been badly damaged beyond repair by careless DIY botch jobs (something you take a risk with when buying from eBay Rolling Eyes ). Usually, if the damage is limited to a just a few scratches I just leave it, but here I had no option other than to completely remove that coating. It left no haze, and I don't think as an AR coating it was a very effective one in the first place. IQ on those lenses seems to be fine, maybe a slight loss of overall contrast but I would have to set up a proper comparison test to be sure.

Polishing off that soft green coating has been a variable experience. On one lens it came off very easy, using nothing more than a lint-free cloth and a bit of water; on the other there were a few hard spots, especially in the centre, and required the use of a small amount of metal polish (either brass or silver polish; can't remember which one I used).


PostPosted: Sat Jun 29, 2024 11:52 pm    Post subject: Reply with quote
RokkorDoctor wrote:

Polishing ......... required the use of a small amount of metal polish (either brass or silver polish; can't remember which one I used).


Very interesting!
What grit those brass/silver polish?
Did you use some sort of contraption to remove the coating? You know, to follow the spherical shape of the lens.
Or just the good, old elbow grease?


PostPosted: Sun Jun 30, 2024 10:14 am    Post subject: Reply with quote
Himself wrote:
RokkorDoctor wrote:

Polishing ......... required the use of a small amount of metal polish (either brass or silver polish; can't remember which one I used).


Very interesting!
What grit those brass/silver polish?
Did you use some sort of contraption to remove the coating? You know, to follow the spherical shape of the lens.
Or just the good, old elbow grease?


Just elbow grease. No idea what the grit is, just standard silvo or brasso, it was one of the two. And only light pressure. The polishing compound used in consumer grade silvo/brasso is not going to be very pure nor will it have been accurately graded, so hard pressure would be ill-advised. The idea is to abrade the soft coating, not re-polish the underlying glass surface.

TBH these were practice-lenses. Had they been valuable or rare lenses I would have spent more time trying to find a "safe" polish. You want something that is harder than the green coating (not hard to find, the coating is soft) but softer than the very thin silica-gel layer left by the factory polishing process.

N.B.: some may be confused by the mention of a silica-gel layer, as it tends to be associated with the silica-gel beads in moisture-absorbing packs. However, the final polishing process of glass also leaves a thin silica-gel layer on the exterior surface of the glass. This layer can be eroded by alkaline ions released from the glass following prolonged exposure to moisture, resulting in a haze that can not be removed without re-polishing the glass surface.

Those interested in more detail I would point to the following books:

"Optics Manufacturing - Components and Systems", Christoph Gerhard, CRC Press, 2018, section 8.2: "Hypotheses of Polishing Processes"

"Fabrication Methods for Precision Optics", Hank H. Karrow, Wiley-Interscience, 2004, section 1.1.5: "Chemical Behavior of Glass - Dimming Cause by Water Vapors"

The mechanical and chemical processes involved in the polishing of glass are still not understood completely and scientific research is on-going. I would love to point to some established on-line research articles but what I could find in a few minute search are scientific research papers behind a pay-wall.

I did find this: https://pubs.acs.org/doi/10.1021/acs.langmuir.3c00304
Post new topic   Reply to topic
Home   DIY
Page 1 of 1