Richard Baker: The first plutonium that, other than the cyclotron that produced plutonium, was made at what was called the Clinton Piles at old X10 down in Oak Ridge. The Chicago Met Lab worked on the micro scale reduction of the metal. This produced rather small quantities but never enough quantities to study its properties in any accurate manner.
At Los Alamos here starting way back in I’d say July of ’43, we started setting up out here, facilities to start working on plutonium and enriched uranium to prepare in first small quantities like half gram quantities and then go up to, say in those days, 500 gram quantities. We started to work out methods of preparing these two metals on these various scales and two purity specifications which were very uncommon in those days as far as metals.
This entailed then a setting up of rather extensive analytical facilities to tell us what we were doing. As half gram and gram quantities of plutonium became available from the Clinton piles the raw nitrate material was shipped up here and Los Alamos started devising schemes for purification, preparation of the halides for reduction to metal and then reduction to metal and then looking into the physical properties of the metal.
The people involved, as I recall, well I know these are the people. In the purification it was Art Wahl ironically one of the co-discoveries of the element.
Stephane Groueff: Wahl?
Baker: Wahl. W-A-H-L. He was the co-discoverer of plutonium with [Glenn] Seaborg and [Edwin] McMillan.
Groueff: At Berkeley?
Baker: Yeah. Then the preparation of the halides was taken on and spearheaded by a man by the name of I.B. Johns. The reduction to metal by myself. The fabrication and all and metallurgical properties of metal by Eric [R.] Jette was in charge of that work.
Groueff: Now who was the head of this division?
Baker: Joe Kennedy. Cyril Smith was his right hand man, but Joe Kennedy was really the head of the division.
Groueff: Was he really a very young man?
Baker: He was a very young man—
Groueff: In his 20’s?
Baker: In his late 20’s. He’s the one that went to Washington University as head of the department after the war and passed away rather soon after that. Art Wahl, by the way, is at the Washington University in St. Louis now and I believe Art is head of the Chemistry Department there.
What we did was use rare earths as a stand in until we received plutonium to try to develop these reduction procedures. At that time, from the small quantities of plutonium being produced in micro scale, the melting point of the metal was very much in doubt. The first half gram quantity of plutonium that we tried a reduction on here was not successful because we reduced it using the procedure for a higher melting point metal and plutonium actually turned out to be.
When we finally gathered together half gram and gram quantities of plutonium is when it became evident that it had it’s many allotropic modifications. The alpha phase plutonium— that is the pure alpha phase plutonium— is a very brittle material and we were very baffled by the fact that, how in the world was one going to fabricate this type of material because by hitting it or pressing it or anything it’s so brittle that it breaks and pops.
It was in that time that we hurriedly started trying to alloy it with something in order to make it more malleable. This is when the recently declassified gallium alloy was first discovered. This was done pretty much under the guidance and all of Eric Jette and this made a material which was more fabricable.
Groueff: What is the name of this alloy?
Baker: It’s an alloy of plutonium and gallium; it has no name as such. After we reduced a few of the half gram and one gram charges we went immediately and the plutonium began coming in. We went immediately to the production of ten gram quantities of plutonium. Then gradually worked up to one hundred gram—no, twenty-five gram quantities. Then went up to one hundred and finally ended up reducing on 250 gram scale.
Groueff: When was that?
Baker: That came along, I can’t remember the real dates, but it was the early ’44 that the material started coming in larger quantities. It was only when we were was in able to go up to the twenty-five and hundred gram quantities that we really began learning about plutonium because we had enough then to really work with. We were able to adjust our conditions to produce it in a reproducible manner.
Actually, in this work of first producing the plutonium and looking at it and all from a real human interest point of view, there wasn’t really anything really outstanding about it. What it really meant was working with an element that wasn’t known, a brand new thing. This gave the people working on it a great thrill technically and all but other than having to work with it in enclosures, which was purely an equipment challenge, there wasn’t anything about the production of the metal that necessarily was of human interest. Just a real technical interest. We ran into these various allotropic modifications, but it was just a terrific technical thrill to be working with something that was man made, no one else had ever worked on it before.
Groueff: Was it extremely difficult compared to other metals that you were used to?
Baker: Oh yes we just didn’t know of any metals that would be as difficult as this. Both from— well the big difficulty with plutonium then and today is this toxicity. You must handle it under complete enclosures, complete ventilation at all times.
Groueff: How did you work with the metal then? In special uniform?
Baker: We immediately went to, what is commonly called in the atomic energy field, dry box enclosures and all. We immediately went to them before anything else.
Groueff: Rubber gloves and those things— so you never touched it without—?
Baker: Oh yes. We never used remote control. We used direct hands. The only thing that we had to protect ourselves from was the alpha and the ingestion of plutonium, not the radiation.
Groueff: How did you protect the face?
Baker: Well we just had the plutonium in a complete enclosure, in other words and worked through the enclosure with rubber gauntlet type gloves. Now, to be sure, the things we did and the way we had to work with it in those early days, was, as one looks back on it, very crude compared to the way we do it today. But fortunately, we did a safe job of its handling. In other words, we did not have any insurmountable contamination difficulty or—
Groueff: Where was this job done?
Baker: It was done in a building called, which is now torn down and buried, called D Building.
Groueff: In Los Alamos?
Baker: In Los Alamos, in the old Tech Area yes, right across from the pond. You could find pictures of the old D Building.
Groueff: How many people were involved in this? In the dozens or in the hundred people or—?
Baker: When I first arrived here there was probably about ten of us. By the end of the war, that is when the war was over, the staff I would guess of civilians was probably up to a total of possibly 200 people.
But then we had a great many of what we called the Special Engineering Detachment [SED], who were military boys that college trained and all that had been drafted but sent up here as scientific people. Only for one reason this was difficult was that is they lived in barracks you see and our housing was very short at the time.
Groueff: What difficulty was another big difficulty? There was something to do with the heating and the metal changing its qualities, its properties, according to the different temperatures; no?
Baker: Yeah that’s the allotropic modification.
Groueff: How would you describe that to a complete layman? In other words change its length or its volume of different temperatures?
Baker: It changes— I guess the way to describe that would be as you heat it up it goes through the allotropic modifications that involve density changes and thus involve volume changes. The thing about this is the Alpha modification is very brittle and if you heat it up to say 120 degrees along in there, the Beta modification is malleable at about 120 degrees so you can work it. But then as you cool it back to room temperature it goes through its volume change and cracks again. wWhat the gallium alloy did, then, was stabilize it in a malleable allotropic modification.
Groueff: So that’s rather unusual difficulty in metals or are there other metals that you knew would change so much?
Baker: Oh yes there are other metals that have phase changes but not as pronounced and near as many as plutonium.
Groueff: You never seen anything like that before?
Baker: No, not to that extent, no. The thing that it did was give us a great deal of trouble because as we— the first plutonium we made wasn’t very pure so that it wasn’t always pure alpha phase plutonium, the first modification. The density kept varying.
For example the density of Alpha— of pure alpha plutonium is about nineteen grams per cubic centimeter. If we got certain impurities in it, it would be lower than nineteen and we couldn’t understand why we were making different density plutonium for some time until we finally got the pure material. Then we were able to heat it up in a volume change apparatus and find out that it had these phase changes.
Groueff: So wasn’t that a tremendous difficulty because you had to work with complete precision and perfection and yet the metal was changing all the time? How did you manufacture later those very highly precision—?
Baker: By going to the alloy where it didn’t change over temperature range.
Groueff: So that was the major discovery. Do you know once you had the metal in quantities what did you know about how to handle it, how to cut it, or how to shape it or how to—?
Baker: Well actually what we did with the main challenge and the fabrication of plutonium metal was to take the ordinary procedures, that are used for metal forming and machining and the like, and adapt them to a complete enclosure operation. That is an ordinary lathe will machine plutonium, but how do you put an ordinary lathe into a complete enclosure and work with it with gloves, with glove ports and all? That was the real challenge; it was pure equipment engineering.
Groueff: Was it difficult to cut or to shape—?
Baker: No, no plutonium machines very much like say brass.
Groueff: So you could give the shapes you want like you would with brass except for this difficulty that you had to handle it always in an enclosed area?
Baker: It lent itself to the regular conventional metal forming operations.
Groueff: Until you found this alloy which helped?
Groueff: Did you find it hard to plate the materials after you heated them?
Baker: Well only to the extent that plutonium is a very reactive metal to moisture and all, but we didn’t find it too difficult.
Groueff: Didn’t you have to use some different tools and, what you call this, containers because of the nature of uranium? Wouldn’t they melt before you melt the uranium? Is uranium melting point very particular—?
Baker: Well you mean plutonium or uranium now? Oh, well uranium melts at say 1250 degrees Centigrade and plutonium melts at about 630. This presented no problems. As a matter of fact, in the casting melting of plutonium, it just made it easier because you didn’t have to go to such a high temperature.
Groueff: What were the difficulties with Uranium 235?
Baker: The difficulties with Uranium 235 essentially were that we had to develop procedures for making it to the purity specifications required. Until we started working on that here at Los Alamos, the uranium metal had not been produced in quantity to the specifications that were required. So we had to develop reduction procedures that made pure metal. Again, we had to— but not to the extent of plutonium— we had to learn how to handle it in enclosures, but it was much easier.
Groueff: Which purification caused more difficulty, plutonium or—?
Groueff: Now is it true that the requirements for purification were something incredible, something one millionth of a—?
Baker: To start out with, the initial calculated requirements for the purity of plutonium were incredible as you say. Very fantastic, practically no impurities in it. But as we went along and calculations and experiments were improved it was found that we didn’t need to have such high purity.
Groueff: But still it was much higher than the standard requirements and metallurgy?
Baker: Oh yes.
Groueff: None of you or your team ever worked with this high standards so that was another extraordinary problem.
Baker: It was an extraordinary problem to think in those terms and also, I emphasize, that to have even developed procedures, analytical procedures to tell whether you’d achieved it.
Groueff: How was it done?
Baker: Mostly by spectrographic analyses, yes.
Groueff: The spectrograph would tell you what impurity in what, in the millionth?
Groueff: Impurity tolerated to incredible small amounts.
Baker: Yes it was thought and we set up initially to try to achieve these very, very high purities to the extent that we started filtering and analyzing the air in our new D Building to see if we could keep all the dust out because the purity specifications were such that theoretically we couldn’t even have dust in the room, you see. I’m not real sure whether we would have, in the time that we had before the war was over, whether we ever met the purity specifications first set up or not. We can just about do it now.
Groueff: When you first, you and your friends, when you were told about the problem and the requirements what was your first reaction about the problem and the requirements? Was it crazy or impossible?
Baker: No, it wasn’t that. It was simply, “Well since we don’t know anything about plutonium and don’t know how we’re going to make it, we had better first find out what the metal is going to be like. How we’re going to produce it and see if we can’t meet those purity specifications.”
The first challenge was not purity actually. It was just to make the material, find out what it was. You see plutonium metal could have been anything.
Groueff: What color is it to the eye?
Baker: Plutonium metal, if the surface isn’t oxidized is a bright metal just like— but it oxidizes and it’s usually unless you keep it in a very, very fine atmosphere, it’s always a dark gray to a black because it gets an oxide film over it. There is one thing I do want to mention before I—
Groueff: Dr. Richard Baker, about metallurgical problems, Los Alamos - Part 2.
Baker: Los Alamos was set up to do a complete metallurgical and chemical job on both uranium and plutonium to the extent that, until after the war was over, all the plutonium produced arrived at Los Alamos in the impure nitrate stage. No one else was able to make the metal in quantity.
The same thing was true of all of the product of the Oak Ridge operations. It arrived at Los Alamos in the form of a fluoride. All the metal, both the enriched uranium and the plutonium, was made here at Los Alamos.
Groueff: In other words, Hanford and Oak Ridge didn’t do the purification?
Baker: They did not do the final purification nor did they produce the metal.
Groueff: They did not produce the metal?
Groueff: They did not produce—
Baker: No. It wasn’t until after the war that we started turning over the processes for making plutonium and uranium metal.
Groueff: I see. How did you receive the-the metal here – both uranium and plutonium?
Baker: We received the enriched uranium as the fluoride from Oak Ridge.
Groueff: But in tubes or in what? In bottles?
Baker: Well that being a dry compound, it was in metal cans.
Groueff: Cans. How big, more or less?
Baker: Well, I forget the amount. I think at those times, when it was available in quantity, it was received in – I believe it was 250 gram lots.
Groueff: That was later. But at the beginning it was just a few—
Baker: Any amount they had.
Groueff: They were sent by courier?
Baker: Yes, it all came by courier.
Groueff: And then it would come to your laboratory?
Groueff: And the plutonium?
Baker: It came as a nitrate, which had been evaporated down to a rather slick, or thick slurry, which was much like syrup.
Groueff: I see.
Baker: And it came in stainless steel containers by couriers.
Groueff: From Oak Ridge or from—
Baker: From Hanford.
Baker: Yes, first from Oak Ridge.
Groueff: The small quantities?
Baker: With small quantities. But then when the Hanford pile started producing, it came in from Hanford and again by courier.
Groueff: Another thing I read I wanted to ask you whether you know about is the tests that they did with different metals for the tamper, they used. They tried—unsuccessfully of course—platinum and gold?
Baker: Uh huh.
Groueff: Now I think that will be amusing for the public—the idea that a piece of platinum was here. Can you tell me where it was brought from or how it came here or – you didn’t work on that?
Baker: No. I just was aware of that. I didn’t know. This man that was just in here, Van Gimmer would know that.
Groueff: I see.
Baker: Because he was in the purchasing and procurement at that time.
Groueff: But you didn’t work with a platinum?
Groueff: You were a—
Baker: My activity was limited to uranium and plutonium.
Groueff: And plutonium?
Baker: Uh huh.
Groueff: And who was giving you the requirements—the theoretical department?
Baker: The theoretical people were giving me the requirements.
Groueff: Dr. Bethe’s people?
Baker: Yes. Bethe, and of course Oppenheimer.
Baker: Was the director.
Groueff: And you worked directly with those people personally?
Baker: Uh huh.
Groueff: Oppenheimer would come to, or you would report to him about that?
Baker: Well, no. What we’d have in those days are, I think the frequency was at least once a week if not more often. There would be meetings at which our problems would be discussed. The theoretical people were working just one step ahead of the metallurgy and chemistry anyway, you see. It was pretty much a simultaneous operation. Calculations and material problems were going on just about at the same time.
Groueff: And once a week you would have conference?
Baker: Uh huh.
Groueff: And everybody would report progress?
Baker: What they were doing, yes, and how they were doing.
Groueff: And who were among the top scientists more personally involved with your side of—
Baker: Well, it would have been Joe Kennedy, Cyril Smith – those two men were heading the chemistry metallurgy division. They were the ones that were working directly with Oppenheimer.
Groueff: Oppenheimer. I see.
Baker: On the materials problems.
Groueff: Where did you come from? From what field? Physics?
Baker: I’m a physical chemist.
Groueff: Physical chemist?
Baker: Uh huh.
Groueff: Where did you work before? How did you happen to be connected to Las Alamos?
Baker: Well, I got connected with Los Alamos through the Ames Laboratories at Ames, Iowa. I graduated from the Ames College—it was then Iowa State University.
I graduated and had gone to work in Chicago. Then when this whole project broke, and F.H. Spedding, who was connected with the Manhattan district with Oppenheimer and all – then just a small group of people trying to get things organized at the Met Lab in Chicago. I might add that the bulk of the normal uranium work for the piles, the work of producing good uranium in quantity for the piles, was then going on at the Ames Laboratory, you see.
Groueff: And they were contract with Chicago?
Groueff: With the Compton people?
Baker: Yes. They were—
Groueff: You worked with Dr. Spedding?
Baker: Uh huh.
Groueff: Dr. Spedding was the specialist in all this?
Baker: Well, no. I didn’t work with Spedding. When this broke and they were going to organize Los Alamos and set this project up, having come from Ames, Spedding contacted me and Oppenheimer to talk to me about coming out here to work at Los Alamos.
Groueff: Where did they see you? At Chicago?
Baker: At the University of Chicago, because I was working in Chicago at the time.
Groueff: I see.
Baker: I had left school, you see.
Groueff: When they came to you, did they tell you what it was about?
Baker: They couldn’t tell me a great a deal. They just told me that it was a very vital defense project and they pretty much told me that it was very, from a technical point of view, very challenging – that they would have no trouble putting me on leave of absence with the company. Pretty much, I joined the project on just what they told me—that it was very important and it would be challenging.
Groueff: You liked the idea of something challenging?
Baker: Yeah. And you don’t question a lot things during war years, you see.
Groueff: Uh huh. How old were you then?
Baker: Well, let’s see. I would have been about 25.
Groueff: You were 25?
Baker: Uh huh.
Groueff: So you were excited about the idea of working on something new and challenging?
Groueff: But you didn’t know where you were going to come?
Baker: Just New Mexico.
Groueff: New Mexico. But not the site?
Groueff: You never heard of Los Alamos?
Baker: No. I’d never been in New Mexico. The only thing I recall about that was that Oppenheimer had a picture with him that was taken during the ranch school days here that showed Ashley Pond over here. It had two swans floating around on it and a canoe. This was taken when the boys were here. By the time I arrived here—
Groueff: Are you sure you it wasn’t a postcard?
Baker: Yeah, a postcard, it was. It looked pretty good. You could tell by the picture that it was in the mountains. And by the time I arrived here, Ashley Pond—due to construction—had been reduced to just one great big mud hole, is all it was.
Groueff: And no swans?
Baker: No. No swans. There were no canoes. They were drawing water out of that for construction purposes. And the interesting part of it was that coming out here, through dry New Mexico, I was wondering where all this water out of this pond and the swans was.
Groueff: And it looked so dry out there?
Baker: Yeah, and it was so dry. I arrived here in June in a very dry time of the year out in here.
Groueff: June ’43?
Baker: ‘43, yeah.
Groueff: So you were disappointed not to see the swans and the canoe?
Baker: Yeah, but that’s one of the interesting things I remember about it. I stopped off actually and waited to be called out here at the Ames Laboratories for about three or four weeks. Then I came out here, reported in. All very secret.
What you did when you started out here like that was you just put your faith in the people that had talked to you, because you really didn’t know what you were doing or where you were going. The interesting part now, as you look back on it as you interview people, to work at this laboratory now you have to tell them the retirement system, the pay. In those days, we didn’t even ask what the pay was.
Groueff: You were very poorly paid, no?
Baker: Oh, yeah. Yeah.
Groueff: What? Something about $400 a month?
Baker: No, I think that when I came here we made $330, and it was all based on when you got your degree. As I recall, the division leader, Kennedy, and I, made almost the same money because it was just based on when you got your degree.
Groueff: So your pay was $330 a month?
Baker: Uh huh, something like that.
Groueff: But, people didn’t care very much?
Baker: Oh, no. Well look, I was single and I came up here, and as I recall, I ate at the Army mess hall and had a dormitory room. I think the total cost was only something like $25 a month for the whole business, you see.
Baker: Well, I think actually, unless you have questions, that’s about all I have.
Groueff: I want to ask you – In Chicago, did you work on the project with uranium and with plutonium?
Baker: No, I never worked on the project in Chicago. For the few weeks I stayed at Ames, on the way out here, I started becoming familiar with the reduction of the rare earths. We knew that this would be one possible type of metal that this material might be like. Since we didn’t have any, just as a stand in material, we just started working on small scale reductions of the rare earths.
Groueff: I see. So you were not in the work that they did where Spedding?
Baker: No. I never really went to work, in earnest, on the preparation of plutonium and U-235 metal until I arrived at Los Alamos.
Groueff: Los Alamos. So from Iowa you arrived first to Santa, for example, no?
Baker: Uh huh.
Groueff: By train?
Baker: Well, you arrive at Lamy by train. I took a bus to Santa Fe. Then my instructions said to go to this 109 East Palace where all of us met Dorothy McKibbin. She made arrangements to send us up by army car to Los Alamos.
Groueff: What kind of office was it and what kind of woman?
Baker: Oh, a very, very delightful person. The office is down in Santa Fe, and it’s a regular business office off of one of the patios in the old buildings of Santa Fe. As a matter of fact, if you could, while you’re in Santa Fe, you should walk over to 109 East Palace.
Groueff: I will.
Baker: Because there’s now on the wall in the patio there, a plaque telling of this. The office was just closed about a year or two ago.
Groueff: So you went there and you met her and you introduce yourself?
Baker: Uh huh.
Groueff: And she gave you the instructions?
Baker: Uh huh. And then the army took us up to Los Alamos.
Groueff: The same day?
Baker: Uh huh.
Groueff: By car, huh?
Baker: Uh huh, by army vehicle. And then when I arrived here, of course, there was no place for me to sleep—no housing. So I lived at the guest house at Bandelier Park down here from Los Alamos for about two or three weeks.
Groueff: Is that far away?
Baker: No, it’s about 15-20 miles.
Groueff: I see.
Baker: It’s a national park, part of the national park system. There’s a hotel and all there, which was closed during the war and used by Los Alamos.
Groueff: And you reported here to whom? Oppenheimer?
Baker: no. I reported to Joe Kennedy and Cyril Smith.
Groueff: I see.
Baker: Oppenheimer is where you start talking at Ames, Iowa.
Groueff: Ames, Iowa—
Baker: Oh yeah, they set up a pilot plant there and produced it – tons of it before Mallinckrodt got started – right on the campus.
Groueff: I see. And you worked there?
Baker: Well, I saw it, but the reason I know this is because of history, but also because I happen to know Spedding and came from that college.
Groueff: I see. That was uranium?
Baker: Uh huh. Normal uranium for use in atomic piles.
Groueff: I see, and here you were the pioneers of the uranium-235.
Baker: And plutonium.
Groueff: And plutonium, which had never been worked on before.
Baker: No, they were both new as far as the preparation of the metal and the fabrication of it, and the development of handling procedures for it.
Groueff: I see. But the Iowa people, Spedding and—
Baker: Were on normal uranium.
Groueff: They’re uranium-238?
Baker: Uh huh.
Groueff: And even producing it in quantities?
Baker: Uh huh. I wouldn’t be a bit surprised, although you will have to double check this – that the bulk of the uranium or the first pile at Chicago may have been made at Ames.
Groueff: Dr. [Norman] Hilberry told me that the top wasn’t—
Baker: We just went to work and tried things with the best scientific knowledge we knew.
Groueff: What was that, with the plutonium?
Baker: This was with both plutonium and magnesium, yeah.
Groueff: And uranium?
Baker: And uranium, yeah.
Groueff: So what was the problem?
Baker: The problem was that thermodynamics said that we probably couldn’t use magnesium oxide as a crucible for the preparation of these two metals by calcium reduction, but we tried it anyways because it was one substance that we knew how to make and we knew how to purify.
Groueff: The crucible?
Baker: The MgO. So we went ahead. The theory said that it probably wouldn’t work.
Groueff: Huh. And you tried it anyhow?
Baker: Just went ahead and tried it, and it worked alright.
Groueff: And you tried it personally, didn’t you?
Baker: Uh huh.
Groueff: And it worked?
Baker: Uh huh. And to this day, it’s the refractor used for the production of metal.
Groueff: Very important step. Oh boy, all the trouble with crucibles. I don’t remember hearing anything about crucibles. For a year almost. Because otherwise you couldn’t find any crucibles?
Baker: Nothing to hold it in to melt it.
Groueff: Why? Because it’d melt? Everything melts it?
Baker: Well, or reacts with it, you see. Uh huh.
Groueff: The crucible of difficult metals before that are made of what?
Baker: Well, I tell you, you take a lot of the refractory’s that were then known and made in the laboratories and commercially at the time we went into this business were simply not pure enough to consider. Actually, as you look back on it, the work we started on the preparation of plutonium and uranium here at Los Alamos really went from the small scale metal work in the field of metallurgy, for the first time, crossed a barrier on purity of metals.
Groueff: Without precedence from before?
Baker: That’s right. Except perhaps copper, but it forced us to start going in to producing pure metals and pure materials to use with the preparations probably for the first time on a large scale. Because we were headed toward making quantity of it, not just small samples for—
Baker: Laboratory investigations.
Groueff: And the nuclear requirements on purity were so stringent?
Groueff: And fantastic from what I understand, there. You could pick up so much from a crucible, you see, if it had impurities in it, it went right into the plutonium or uranium.
Baker: Say, there is one thing that is of interest that you should know. I just thought of it when we started talking purity. We built this building as I told you, the D building, filtered the air, but then we wanted to know how much dust and what elements were getting into it. So there was a man sent out here from the Smithsonian Institute, and you must know his name. He was a buddy of Charlie Mitts’. He was a microscopist from the Smithsonian Institute. He came out here and worked during the war with his microscope, identifying the dusts that were coming in our D building.
Groueff: Because even dust was a problem?
Baker: Yeah, because we were worried about the dust coming in and getting into our materials and adding impurities.
Groueff: How did you eliminate the dust or the danger of the dust?
Baker: Just filter as we sucked the air in and filtered it.
Groueff: Uh huh. Kind of air conditioned room?
Baker: Uh huh. But in those days, twenty some years ago, filtering of air coming in a building to get it dust-free was a new adventure.