What is the magical ingredient in U340 to block IR and can we all petition Hoya or Schott to triple it?

[dabateman]

I have been analyzing the 2, 4, 6, 8, and 10mm thickness plots from what Cadmium has provided from the Schott filter program and Jonathan's actual collected data using a spectrometer.

You can do this at home too with the Schott filter program. Type in 3mm thickness, then 6mm and you will see the IR leak drop 2 orders of magnitude. Use 4.5mm the half way point and it drops one order of magnitude.

But the UV spectrum only drops 5% to 10% over these changes.

So what is this magical glass ingredient?

Can we collectively ask Hoya or Schott to tripple it to give us 2mm or 4mm thick glass with excellent IR blocking and great UV transmission.

 

Just a thought as I am concidering kindly asking someone for 4mm or 6mm thick U340 in the future.

[Stefano]

Yes, I think that Hoya U-340 is the best U glass that exists. Quoting from Wikipedia, "Wood's glass is special barium-sodium-silicate glass incorporating about 9% nickel oxide". I also asked myself what is the chemical difference between U-360 and U-340 type glass. If you compare Schott versions (UG1 and UG11), Hoya versions (U-360 and U-340), Optima's ZWB2 and ZWB1, and so on, they all have similar characteristics. Also, how does Schott achieve the UV performance of their S8612 filter? What is the chemical compound in BG glass in general?

 

So, if I understood correctly, do you want them to make a "denser" version, so that, say, a 2 mm filter equals a 4 mm "old" one?

[dabateman]

Not denser, just more of what ever is exponentially blocking the IR leak. This would also get to your glass wish with very low IR leak and high UV transmission.

 

There must be a technical difficulty why this hasn't been done. As the Astro community will pay $500 for a Astrodon or $400 for a BaaderU.

The UV community similarly will pay for it. So must be a technical issue.

Or they are not paying attention and missing a market.

[Stefano]

Imagine if they could mix U glass and BG glass and make a ready-to-use UV only glass. It wouldn't be better in UV transmission and IR rejection than a common cemented stack, but it would be surely cool to use.

[Stefano]

Maybe too much colored glass would be very fragile (Wood's glass, which is basically that kind of glass, is already not very mechanically strong).

[Cadmium]

Don't you get the reason?

UG2A and UG1 are examples of this idea. UG1 is a 'stronger' version of UG2A. UG2A is a weaker version. They are 1 (UG1) to 1/3 (UG2A) in relative strength or density.

The reason they don't make a U filter with stronger UV transmission compared to stronger IR OD suppression is because the mixture of compounds are balanced the best they can already to do just that.

Otherwise, I am sure glass would exist like you are imagining ages ago.

If you just want a stronger denser filter to block IR with no stacking, then the 8mm U-340 works, of course reducing the UV strength compared to 2mm thick version.

If you want a very high UV transmission with a very suppressed IR then I don't think that is possible unless you go dichroic.

 

[dabateman]

Cadmium,

I don't see the range for the Ug11 glass. Like BG40 2mm is similar to 1mm S8612, but S8612 goes deeper into UV. And the comparison between BG38 and BG40 at various thickness.

Or th KG series, where 2mm thick equals 1 or 4mm thick up the line.

Yes Ug1, is like Ug2.

But I don't see the Ug11 equivalent. No matter howmuch or how little you stack ug1 and ug11 they will not be equal. So there formula is clearly different.

I want a thinner say Ug12 that has the IR suppression of twice as thick Ug11.

Did that make sense?

[Cadmium]

I don't think there is any 'watered down' version of UG11.

UG11 and UG1 are not the same glass mix, they obviously have a different basic recipe.

They don't make UG12 anymore, and it didn't have good suppression in the visual range, nor did it have as deep of transmission as UG11 or U-340.

 

From the JENA GLASWERK SCHOTT & JEN., MAINZ "Color Filter Glass" book, Page 16.

[dabateman]

Wow,

I have never seen that before. I thought I was making up Ug12 just for my example.

Ug1, ug2, ug4, ug12 and ug14 look to all be from the same family.

This plot seems to indicate that Ug5 and ug11 are in the same family.

Looking that ug11 might be double the density of Ug5. As there is two stops loss in IR and only 7% loss in UV signal.

 

I wonder if they double it once more for a mythical Ug22, if the Uv would just drop to 80%, with a much better IR suppression. Then getting a 4mm thick of this mythical Ug22, would equal 8mm ug11.

 

Before you posted this what I thought you may have been saying is that Ug1 and ug11 are the same family, at double the density. So the next drop would move to peak max 320nm and end at 360nm, which isn't useful to too many applications. But this plot clearly indicates two seperate glass families. I wouldn't have guessed Ug11 was related to ug5, but that looks correct from this.

[Andy Perrin]

What, UG12, UG14?? This is like seeing dinosaur fossils of a new species for the first time!

[Cadmium]

UG1 and UG11 are in the same 'family', being both U glass that transmits UV and also 700nm, but not the same glass recipe, even if adjusted by thickness or 'density' (thickness is really just 'density').

However my example using UG1 and UG2A was to illustrate how those two are about the same glass recipe, just that UG2A is 'watered down', 1/3rd the strength of UG1.

UG5 on the other hand, indeed has a robust 300nm inclusion, more so than UG11/U-340, however it has too much visual to be used as a U-only filter.

 

UG5 and UG11 are not the same visual transmission at any thicknesses/density. UG5 has a tapered visual transmission, but UG11 does not.

No such thing as UG22 as far as I know.

 

By the way, personally, I would use U-340 8mm instead of 6mm, because you get better OD suppression and don't loose that much UV band width or peak amplitude.

I think what you loose with the 8mm is worth the OD5, and from what I have tried, it is sharp.

It doesn't come in 6mm or 8mm, unless you have a slicer, and you get blocks, the sheets are 4mm thick, so it requires gluing or just two filters screwed together, both look fine.

If using glue, then you will need to use a glue that transmits low enough for the stack. If you want thicker than 4mm, 6mm, 8mm with no stack or no glue, then you get that from ITOS, they have a slicer,

but it will cost a lot more.

 

[dabateman]

My thinking for a 6mm u340 was that might be the maximum thickness that my 1.25" ring can handle and still clear my filter wheel. But I need to accurately measure it.

Then wondering if a 28mm in either 6mm or 8mm is possible.

I do have a thicker ring now that still clears my wheel. But haven't measured it.

 

[JMC]

Steve, thanks for sharing that old Jena information. I recently found a filter supplier in the UK that had some small samples of old UG2, UG3 and UG12 on their shelves, so I have asked for them to be made into filters for me. I was struggling to find much (or any) info on them online, so at least this covers 2 of them.

[Andrea B.]

Magical ingredient must be one of these??

 

[Andrea B.]

Stefano: I also asked myself what is the chemical difference between U-360 and U-340 type glass?

 

Here ya go!

Just add some arsenic to get U-360.

So we should not be licking our U-360 filters !!! :wacko:

just kidding........

 

[dabateman]

Andrea brilliant.

I hadn't thought to actually compare the safety data from the MSDS's.

But as I know as I used to manage these once for a company. There maybe one or more ingredients listed that actually is not in the product or added to the product. Sometimes its just there from a mixing tank or its not there at all, just included to through off the competition.

 

That said your U340 sheet is missing silica. So I will have to confirm that. But that might be the secret ingredient. Its not SiO2 based, like Ug5 and U360.

 

Here is UG5, its different as well:

[Andrea B.]

U340 is made from phosphate glass, it seems.

Linkie: https://en.wikipedia.org/wiki/Phosphate_glass

[Stefano]

U340 is made from phosphate glass, it seems.

Linkie: https://en.wikipedia.org/wiki/Phosphate_glass

"Normal" glass wouldn't transmit that deep into UV.

[Andrea B.]

The Schott UG11 which corresponds to the Hoya U-340 is also a phosphate glass.

 

 

[Andrea B.]

Stefano: "Normal" glass wouldn't transmit that deep into UV.

 

No, it certainly does not.

I made some notes here about lens glass types and transmission range. Some normal glass is included.

[LENS] Approximate Transmission Ranges of Various Lens Glass

[dabateman]

"Normal" glass wouldn't transmit that deep into UV.

 

There is no such thing as normal glass. There are many different types of SiO2 glasses. Including fuzed silica and quartz, both of which transmit deep into UVC.

 

Borosilicate, was one of my favorite glass types when working in the lab. Its one type of Pyrex.

There is a Corning museum in NY with 100's of different types of glass that I still need to see one year.

[Stefano]

There is no such thing as normal glass. There are many different types of SiO2 glasses. Including fuzed silica and quartz, both of which transmit deep into UVC.

 

Borosilicate, was one of my favorite glass types when working in the lab. Its one type of Pyrex.

There is a Corning museum in NY with 100's of different types of glass that I still need to see one year.

Yes, that's why I put " " around "normal". I should have said "typical" or "common". Fused silica and "glasses" (do you consider them glass?) such as CaF₂ are definitely not common.

[Stefano]

Including fuzed silica and quartz, both of which transmit deep into UVC.

Aren't they the same? If not, what is the difference?

[Cadmium]

https://abrisatechnologies.com/2012/10/fused-silica-vs-quartz/

[Stefano]

https://abrisatechno...lica-vs-quartz/

Thank Cadmium.