AVS Historical Persons | Richard Denton - 1990

Richard Denton - 1990

Oral History Interview with Richard Denton

Interviewed by Collin Alexander 1990
 
ALEXANDER: Richard Denton, I understand that you're one of the fathers of this American Vacuum Society, and you had been working in vacuum for a number of years prior to the formation of AVS. Could you tell me how you got started in some of the early things in vacuum and in whatever is involved. 

denton.jpegDENTON: Actually, the first time I worked with vacuum was before I actually got into high vacuum. I was a printing chemist. We got involved with a great big steam injector system that produced a millimeter [of mercury] or something close to a millimeter within a chamber that takes water out of the printing ink that we were working with. We learned a little bit more about what vacuum might do than I knew before. Then, when the war came along and I went to work at the Frankfort Arsenal in Philadelphia. I was brought there to try to get the chemical things that they used in making optics brought up to date so they could end up with 90% of the lenses that would pass inspection instead of 30% or 25% due to scratches. So my first six to nine months there in 1942 was involved in getting these things straightened out, which I did fairly readily. 

Then, toward the end of the year, the Army became aware that the Germans had coated lenses on their optics and that they could see our people maybe half an hour or three-quarters of an hour earlier in the morning and later at night than we could. Surprisingly enough, a great deal of the work of developing the coatings was done in this country by such people as John Strong, and Cartwright and Turner, and so on. So the Navy was already working on it. A fellow named Dr. Lyons had developed a workable process. 

I spent most of the time between Christmas and New Year, 1942, visiting the places that you could hope to learn anything about, which was the Naval Gun Factory in Washington with Dr. Lyons and Bausch and Lomb. I don't know if I saw you up there in my first visit or not, but I'd been there several times on another problem. I saw Dr. Frank Jones, who was head of the chemistry department. I went to Kodak. I think I went to Bell and Howell. They weren't doing much. Practically the only other places in the country that were doing any vacuum coating at that time were Evaporated Metal Films in Ithica, who were making mirrors. I don't think Liberty Mirror had hardly started at that time. There was a company on the West Coast, and they had patents. But I never actually saw anything from there, and they dropped out of the picture. 

So back to my trips. I wrote a report and told them what we should buy and that they should expedite it as fast as possible, and they did. In April, we were coating lenses. That's how I got started.

ALEXANDER: Where did you have the opportunity at that point in time of buying things?

DENTON: Well, there were only two companies that had anything that we could use. One of them was Distillation Products in Rochester and the other was National Research in Boston. So I remember Dr. Jones was advising me - he wasn't directly into coating. I said, "I hear there's a lot of trouble with these systems," and I'd been trying to figure out how many we'd need for what they say our production is going to be. I said, "Can you really rely on this stuff?" And he said, "Dick, figure that 25-33% of your capacity is going to be down for repair at all times." So I figured we needed three systems, so I bought four 18-inch bell jars, two from National Research and a double unit with two 18-inch bell jars from DPI1. Then I enlisted Tom Scatchard, who was at that time assembling instruments - he's a very good mechanic - to run this. I don't think we ever were as bad off as Dr. Jones told us, mostly due to Tom's good work on them.

ALEXANDER: How long did it take you to make a run, so to speak? 

DENTON: Well, the hot coating took us about an hour. 

ALEXANDER: That was pretty rapid in those days, wasn't it?

DENTON: [Laughs] Yes, it was. We were happy to get to 10-4 [Torr] in those days. But the heat was a great help. We could never have done aluminum, I think, in those systems; good aluminum at least, without other methods of cleaning the glass that we were using. The heat did a great deal.

ALEXANDER: If your cycle time was an hour, did you have high-vacuum valves in those days, at that point in time?

DENTON: The National Research system did not have a high-vacuum valve. The Distillation Product systems had six-inch pumps. They had high-vacuum valves, and they had two pumps and they were equipped with, I think they were the one and a half-inch Kinney valves. Kinney2 made high vacuum usable by putting bellows into OIC - Ohio Injector Corporation - valves. You had to be careful with the piping, but one Kinney pump backed two diffusion pumps. This led to some problems. You had to be pretty careful, if you had a system under high vacuum ready to coat, not to start roughing the other one. Not really roughing it, but turning the other diffusion pump into that system with a higher pressure. We found out a lot of those things very quickly [laughs].

One interesting thing that occurred when we were doing it with hot coating. We had Dr. Lyons down at the Gun Factory who had suggested a Munsell color chart to determine whether the coating, which was just single-layer magnesium fluoride, would pass. Of course, we had a General Electric Hardy spectrophotometer there. That was one of the very early spectrophotometers, but we didn't have much access to it. We were in a research place, and it was true all over the country - there were no spectrophotometers. So what they used was this color, and for a single layer of coating you could determine the thickness by the color.

ALEXANDER: How would you do that?

DENTON: By measuring the reflectivity from a lamp, which we held over the top of the system and looked at the reflector, usually a flint lens with a higher index glass, which gave a more saturated color. One of the interesting things that came up then was that, when we got the straw color, it was on the borderline of not being thick enough. As the coating got thicker, the color went from straw to an orange to a rose, reddish color, then blue started to come in as the curve moved, like a boat moving down the canal, which was the high vacuum, so this is the optical spectrum. Then it would get blue. But Tom found out one day - I don't know just how he did this - that the lenses came out white. I guess he got a fingerprint on one or something. He discovered that he could sort of wipe along the side of his nose and put it all over a lens, and he got a couple of molecular layers of some kind of grease on there. I guess these were like 18 angstroms each or something of that order. Actually, if you wiped it over very carefully and then cleaned it up normally, you could raise the coating thickness from non-acceptable to acceptable, by making it optically thicker. Of course, once we got involved with this, we stopped doing that very quickly.

But an interesting thing was that when you took the system lens right out of the hot vacuum and did this immediately before anything else, such as air or water vapor, had absorbed on the surface, why, they lasted a long while. If you really wanted to clean it off, you just couldn't do it with solids. You just couldn't wipe it off. It's just a byline. But the surfaces that we ended up with in the hot thing were really quite pure surfaces.

ALEXANDER: Were anti-reflection films and this type of thing the only types of coating you did during these early days?

DENTON: Yes. That was the only thing that we were required to do. At that time, none of the specifications were on the instruments. They weren't even written about anti-reflection coating. That was changed right away in 1943. But there were only a few mirrors on the instruments that we used. Some of those were chemical silver, and they had to be very special because they had to have the right chemical characteristics so the silver could be carved and cut to make a certain type of sketch on them that was used in range finders. But only when a new anti-aircraft viewing instrument came out did we use any mirrors at all. They actually were done by sputtered chromium at that time, or evaporated chromium, which was done by Evaporated Metal Films3. But we never had the requirements during the war for front-surface aluminum mirrors, as they're known today. 

ALEXANDER: Well Richard, after the war was over, what particular interesting events did you encounter?

DENTON: Everybody was laid off at the Frankford Arsenal. The first interesting event was that I had to eat. So I started looking for a job, and at the same time, Tom Scatchard and I had been talking about setting up a business. Actually, just before the end of the war, I had a busted appendix and I was in the hospital for ten weeks. Fortunately they didn't throw me out till December, so I had time to recuperate. 

I got back to work after the war was over in September. We made up a vacuum system. We had been sent around during the war to people, particularly to people to who we had rented a supply of vacuum equipment. They4 had bought 20 systems from National Research to put in contractors' places. We had to go and teach them how to operate these systems. In my day, this was done by a colonel who was an acute businessman, without any advice from me, who had gone through this, as to which systems to buy. Actually, due to the bigger pump and better conduction, the DPI systems were somewhat faster. I have a feeling we might have chosen them. But they bought these things, so we had to go around and teach people to use them. But we got to know an awful lot of people. 

So when the war was over and we wanted to have a vacuum system of our own, Tom was able to machine base plates and things because he was a member of the Amateur Astronomers club of the Franklin Institute, which was only a couple blocks from where we lived. So he did the work there. Then we contacted people that we knew that had surplus pumps. They had spare pumps and things, and we bought a mechanical pump and a diffusion pump and things like that.

ALEXANDER: This was about when? 1946?

DENTON: Yes. Well, actually, Tom got thrown out of the Arsenal a little before I did. So we really started business some time in December 1945, but we got going in 1946. Most of what we coated then were actually existing camera lenses and binocular lenses, because there were no coated lenses except military. We also did some eyeglasses. People were quite impressed, even with a single-layer magnesium fluoride coating, particularly on the high index lenses that they used for people that were very high myopes. There was some sale of those. 
So we got started with our one system. The next year, we built a couple more and we started to get some commercial work from people making lenses. We got an equipment order in 1948, then we started building equipment.

ALEXANDER: And your organization was called what?

DENTON: Optical Film Engineering. 

ALEXANDER It was a supporter of the AVS at the beginning, I think. I don't know if it's in the program, but it's in the records. 
And you sold mostly high vacuum equipment for optical coating?

DENTON: Optical coating, right. Then we, through a letter that Tom wrote, found a fellow up at Easton TA, General Analine and Film, called Frank Hamm. 

ALEXANDER A new technique, which was developed by Robley Williams, who was one of the founders of Evaporated Metal Films3; he was an astronomer. 

DENTON He had done vacuum coating in Ithaca when he was a professor at Cornell, then he moved to Ann Arbor, Michigan, to the University of Michigan, and he developed a technique known as shadow casting, because of his vacuum knowledge, to improve the contrast and so forth of electron microscope specimens. 

In any event, the people who had an electron microscope now needed a small vacuum system to prepare their specimens. We built this one for Frank Hamm. He searched us out because he had decided to build one, and he bought pumps and gauges and things. He had no idea what to do with them. So we put that together. Then we got in touch with some RCA people who were building electron microscopes. They had been building a vacuum chamber. They found out that they had a rather big mistake in their cost accounting, so they stopped making them. And then we fell into some of that, and that's how we got started in that field, which we're very strong in today, still. 

ALEXANDER: That brought you up until the American Vacuum Society, initially known as the Committee on Vacuum Techniques. 

DENTON: CVT. It always amused me that the origin of that - and there are other people, I guess, that were closer to that, maybe, than I was, if they're still alive. I think with that Society, the original rules were you paid your money and attended the annual symposium. Then you became a member. But if you didn't go to a symposium, you weren't a member. That was changed to the AVS later. Do you remember that? I thought it was not the best system, but I didn't complain. 

ALEXANDER: But it was a way to get started.

DENTON: Yes, it was. I was just so happy that we were able to get something started.

ALEXANDER: As far as I'm concerned, that's a start. Do you want to…

DENTON: That's a lot more than you need, I think. 

Notes
1. Distillation Products Inc., Rochester, NY
2. Kinney Vacuum Products Inc. Boston. MA
3. Evaporated Metal Films Inc., Ithica, NY
4. US Government

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