The above title is a sequence of words that has undoubtedly been uttered, and by “uttered” I actually mean screamed, by every mother on the planet or any other planet……possibly also uttered by many wives to their husbands as well. Wives and mothers can see dirt and clutter that no husband or child is physically capable of seeing. If you can’t remember your own childhood, just observe someone else’s and it will become apparent. Toys not put away, dirty clothes, the mud tracked in, etc. Invisible to the kids, but always immediately visible to the mother. Always. Every. Single. Time. It is almost as if they have an extended spectral range in their vision that allows even the most microscopic dirt to be revealed in glaring contrast to the surroundings.
Of course this is not really the case. And kids and husbands actually CAN see dirt. Many times they just choose not to. I know I can spot the tiniest of dust particles on a bearing surface when putting an engine together…….and then be completely blind to the oil stains on my blue jeans as I prepare to leave the house for dinner someplace nice. No wonder we are such frustrating creatures to have around.
Prior to being interrupted by plumbing repairs and earthquakes at the end of November, I had set out to work on a viewing device to help determine if impurities were present in a completed neon tube. Now, having some time, and since the last aftershock ended an hour ago, I am resuming this effort.
The 1935 book, “Neon Signs” by Samuel C Miller and Donald G Fink is a classic on the subject and spawned a series of subsequent versions over the years, each of which has a few minor additions or subtractions of information. One such oddity in the 1935 edition is in chapter XIV “Tricks of the Trade.” This deals with a situation wherein a completed clear red neon tubing unit may appear fine (ie: it lights up the correct red color, not pinkish or pale) but actually contains impurities that will degrade its performance and life. Such impurities would likely be in the form of gases other than the neon and they would have their own visual color emissions when ionized…..IF you could see them. The trouble of course is that unless the failing is severe and obvious (the “pinkish” color) the overwhelming pure red being emitted would likely mask the other light spectra being emitted. If you have surmised that we are going to look at using some sort of filtering arrangement to block out part of the red light so the other light becomes more apparent then move to the head of the class!
The suggested trick was to employ a couple of layers of blue cellophane and green cellophane to construct a viewer. This would effectively block most of the red light. But blues or greens would have a better chance of getting through and becoming visible. If the tube was good, there would only be the red coming through…if not, the blues or greens would appear. Now, do keep in mind, this will only work on a CLEAR tube filled with NEON. It will not work on a coated tube or one with an Argon or mix fill so its usefulness is pretty limited and so my interest in it is purely from the historical and academic angle…..I am, afterall, the “Neon Archaeologist” and so when presented with such a puzzle I must pursue it.
All well and good, but lacking colored cellophane…..something I’ve not seen around in many years, I opted to use what I do have: Camera filters. The wavelength transmission ranges of the vintage cellophane pieces are an unknown….but it seems a reasonable guess that a blue color correction filter (used for shooting daylight balanced film under tungsten lighting) and a green filter (used for b&w photography outdoors to increase contrast) might work.
The next challenge is a test unit for comparison purposes. I obviously need a “good” one…made and processed as well as could be done…….and I need a “bad” one…not so bad as to be obvious….but just “good enough” to visibly look right but still be defective. That can be made, simply by slowly adding some other gas, even air, in minute quantity while the unit is still on the pumps and doing so while connected to a transformer so it can be visibly lit but not degraded to the point of turning the pinkish color…….or even done by not fully processing it prior to filling.
So with this methodology in mind I planned to produce a couple of units specifically for this test….but then I remembered that I had done some other experimentation before that may yield the needed results…and since I am a hoarder, stuff like this gets tagged and documented but not always tossed out……so I placed this experiment and a known good unit on the table and connected them to a conventional magnetic transformer to light them up.
Both appear red to the naked eye when illuminated and are shown below.
But… One was processed correctly and one was not. To the unaided eye, they both look fine. But one is not. One of them was processed using a far lower bombarding current than is normally required. Instead of being connected to the usual bombarder it was processed using just a 30mA transformer. As a result, more time was spent processing it, and the normal target temperatures for the glass and the electrodes were never reached. This most certainly left some impurities in the tube and while it looks good for now, over time it will most certainly meet a premature failure.
Again, they both look good to the naked eye, but when viewed through the filters, they do show a difference. A very slight one. But enough of one that you can see it. Hopefully you can see it on your screen too. Otherwise you’ll just have to take my word for it. One disadvantage of using a cell phone camera is that it attempts to auto-expose and correct for everything, which is not useful in this application. Oh well. …its the tool on hand and when the limitations are understood, it can work.
The above contrast can likely be improved upon with a darker blue filter. In addition, shooting the photos with a full manual controlled camera would be helpful as well. If you attempt to reproduce this, these are the changes I would recommend. Even so, I was able to see the slight change with the filtration even if the phone pics are less than ideal.
So, you can tell there are some impurities. But you cannot tell what they are. Maybe you don’t really need to know, but being the curious type I want to know…..and besides, if you know what the faults are, you can make better progress towards isolating them.
To get a better idea of what is in there, you would need a spectroscope. A basic spectroscope operates by sending the visible light through a prism which splits it into the common rainbow visual appearance…a grating and a scale will allow viewing the spectral peaks in a way that you can estimate their wavelengths and based upon this and the pattern of spectral lines you can identify some of the materials present that are contributing to the visible light.
Other gases would introduce other lines and visual colors into the spectrum, even though the predominant color appears the same to the naked eye.
In my attempts to use a small pocket spectroscope, I could see this in the different tube units. Way cool! But, I could not really take a good set of photos of it with the phone. What I got was mostly blurry but if you can see the difference, then the exercise was not a total waste. Perhaps I will play with this some more another day…..using a microscope adapter would allow attaching this to a “real” camera and then the exposure and focusing would be far better.
But if nothing else, perhaps this was entertaining for you….and it gave me something to ponder and do today. Now….Go clean your room before your mother sees the mess you made.
Robert, a masterpiece of reason