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Hi. Yes, you may say a concrete block to scrub with. Was more inclined to a (finely powdered) alka-seltzer type of compound to be mixed dry with Portland cement; to release microbubbles at the moment of wetting the mix.... A cheap sodium bicarbonate type of compound. Miguel

Hi. What compound would be the most convenient to mix with mortar to expand it to a very lightweight pumice type end product with non-toxic microbubbles? I say micro because I believe that if the bubbles are somewhat large, would surface too easily before the cement cures. Thanks, Miguel

OK. Thanks for responding. The ions would cross the barrier even if the liquids are non miscible ? If the bottom liquid with its +dopant is applied as paint to a metal substrate and left it dry, then the non miscible other liquid with its -dopant painted on top; when dry wouldn't it be a PN junction ? Miguel

Hi everyone. As a doped silicon junction generates a current when photons strike, how could a pair of ¿non-miscible? thin liquid compounds be formulated to generate current under sunlight, each with its electrode ? electrode1 -------xxxxxxxxxxxxx floating layer electrode2 -------zzzzzzzzzzzzz sunken layer Miguel

Hi. What interesting thing to do with it ? It's a light green powder in a glass vial; the box is marked as "radium" and intended to mix with a clear glue also supplied in the kit. Am still alive (I think) after that stuff has been in my house for 30 years. Miguel

Then, from your statement, if aluminium is sawed off/scraped while under water, will yield a nearly explosive or violent reaction ?

Hi. Just found out that acetic acid (vinegar) applied onto recently scraped magnesium will bubble and fizz. It will not happen on aluminium. That's a household chemical easy to try with. ¿Does it make sense? I will try later myself... Thanks, Miguel

Hi. Re-trying to reply, as the text dissapeared while posting... Try a black-matrix LCD VGA display (I have a couple around, has normally shut pixels and will open the commanded ones) with the backlight panel removed, driven on a .pps -slide show- PC program to select a sequential chain of apertures and its locations. I do not see any problem with the source being infrared, but cannot tell for sure what opacity would be achieved. With plain white light they are not that much of opaque, it may actually be better with IR, or polarized IR! Good luck, Miguel

Hi. Give this a look : http://www.dave-cushman.net/misc/mannject.html Miguel

Hi calbiterol Then it would be a flood infrared source, or a divergent laser.. Put your bib on ; the shutter array from Flixel is here: http://www.electronicproducts.com/ShowPage.aspSECTION=3700&PRIMID=&FileName=sepOL1.sep2003 And you may use Thin-Film-Transistor TFT if LCD is not desired : http://www.hackaday.com/entry/1234000167030541/ Enjoy, Miguel On the post pre-view the long Flixel link did not show up complete; trying again: addthethreew'shereelectronicproducts.com/ShowPage.aspSECTION=3700&PRIMID=&FileName=sepOL1.sep2003 -If does not show well, search for Flixel and electronicproducts- or shutter array and electronicproducts

Hi. Cannot find how to discern if an unmarked automobile wheel is magnesium or aluminium. Any sure way to test please ? If a drop of battery acid is applied to an alloy rim, what reaction, color, etc. is expected if aluminium or if magnesium ? Or any other simple way to tell ? Thanks, Miguel

Hi calbiterol. What dimension is the preferred for the grid array, and how many vertical x horizontal cells ? Is 1mm² per cell small enough ? Is the laser focused to a cell or floods the array ? What is the preferred intercell gap dimension ... 0,1mm? What transparency range from closed to open (light transmissivity at both states)? What shutter speeds ? Same project appeared in other electronics forum about a year or two ago. It may be called a shutter array Miguel Am from Barcelona, pretend to know something, sometimes.

Hi. Battery was an improper term, it will be a single cell (two rods or plates) protuding from a PVC pipe housing the electronics, exposed to seawater flow, submerged at no less than 10 feet depth. A photocell turns the unit off at nights. What would be the reaction ? If C and Zn, Na+ and Cl- Miguel

Hi everyone. From what I remember, the highest electronegativity differential between two metals, the larger the voltage obtainable in a battery when those metals are used as its anode and cathode. Did I remember well? Using easy to get and cheap materials; as aluminium, copper, iron, carbon, lead, zinc... which two would yield the highest potential ¿lead and copper? Am trying to build a simple seawater cell to activate an ultrasonic beacon at expense of the electrodes. An electronic circuit transforms the cell output to a higher voltage for circuit operation. Current capability is proportional to electrodes area. Thanks, Miguel

Hi. How many millions of years has our sun been burning ?... All that mass reduction being consumed to radiate energy for that lenght of time, has reduced its gravitational force attraction, and keeps happening, is it? Then, its pull is not a constant ! For the earth to maintain orbit on a decreasing solar gravity pull, the orbit diameter has to continuosly diminish accordingly, does it ? Or the orbiting speed slowing, does it? Miguel

Hmmmm. Naming as a compass the points on the drawing to have some reference... Being N&S an independent voltage source from W&E ; the positive S is such only respect to negative N. The positive S has no potential respect to either W & E and no arcing should occur in that direction. Miguel

Hi. If I understand the graphic, the high voltage sources being paired in diagonals, the double arcing will occur in cross fashion, as sources are independent. Very good question, I suspect there will be collision of the arcs. No attraction, no repulsion, just crossing paths sharing a central point. Start edit, adding : <Re-thinking,... each arc creates a magnetic field which would affect the crossing point position of each other by forced deflection, and the polarity would determine if one arc passes above or under the other on direct current. Then there would be repulsion or attraction due to magnetic and not to electric fields. If alternating current, there would be a alternating cross path above and under. A similar behavior is an oscilloscope in x/y mode. Vertical defflection plates do not affect horizontal deflection plates electrically.> end edit Perfectly controlled conditions to do the experiment may be unstable. Please come back with observations. Another similar situation could be a neon tube cross, with independently powered straight arms. Miguel

Hi. Yes, an electric eel. Miguel

Hi. Once I browsed a ~400+ page book of formulas with the detailed procedures to manufacture hundreds of real generic commercial products, I remember was over $2000 and well worth them. Examples: formula and process to make brake fluid, detergent, artificial pigment, fly-sticky paper, deodorant, chlorine for pools from seawater... all kinds of things... It is not a household remedies book. Cannot remember the publisher, author, title. Any clues ? Thanks, Miguel

Hi. A refrigerator compressor makes the best of all easy to get vacuum pumps. It really sucks ! You will be able to distill at room temperature. Many are discarded in good working condition. Get one, the size of choice, it is simple to plug and runs nearly silent and u$ually free. Keep its rubber mounts. Miguel

Hi. It is a common suggestion to get rid of ice on a windshield by pouring cold water on instead of warm; there has to be a relation to the behavior Am from Barcelona too, and I pretend to know something... sometimes. Miguel ¿Why do my posts show a checkmark on rating? I have not done anything bad !...

Hi. No.- water vapour, water, heat, cold, did not cause any alteration to the tinting; neither was affected by window cleaners nor showed any aging. At edges where the deposited film remained thicker, it was clearly observable micro puddling areas and dried beading. Was not water based. Imagine wetting an almost horizontal glass, water runs off but the lower edge forms a thicker non-running bead by whatever cohesion reasons. This was no Mickeymouse film job at all. Am very sure it was a liquid applied onto the glass surface. I had a conversation with the person that developed the product and there was not much magic in it; he just had his successful formula and made a side living out of it. The reason the glass had to be removed and laid flat to dry the ink was exactly because was so thin and fluid, that could not be applied to vertical surfaces as most of it would drip and make a big mess. Most customers were reluctant to have the glass dismantled from their cars, but the guy was soooo good, experienced and careful not to miss a clip or lose a screw and keep alignments that I had zero problems, zero complains about the job. The only similar process I am aware of, is gradual tinting in "degradé" done to eyewear lenses, were the lenses are repeatedly vertically dipped onto a solution, at gradually different dephts to dye the upper portion of the lenses darker. Seen it done. Miguel

Hello. 20 years ago, I had my car windows glass tinted overseas by a guy that removed the glass from doors, applied an ink to the inner surfaces by dipping -or spilling onto- (masking the exterior surface); let 24 hours to dry in a dust-free place and reinstalled them. The somewhat involved job result was a superb, yes, superb hard surface with no visual distortion, scratch resistant, UV filtering and unable to peel off. There was half a dozen hue choices in smoke, grey, clear, goldish, bluish, greenish... Several years later, by accident, a bottle of alcohol leaked inside my car parked under the sun and some areas of the ink "crackled" with the fumes. Does anyone knows how to prepare such product? Or ever heard of such process ? Thanks, Miguel [edited: changed the word "crackeled" to the appropiate "crackled" to accurately describe the effect of solvent fumes]

Hello, thanks for responding. Good question; I did not consider this dye to be too dangerous as was to be prepared by young experimenters with common sense in that book from the fifties/sixties; but realize the world has changed a lot since and it has to be taken in account. If there is a choice, would like to avoid caustic, poisonous and restricted access chemicals, maybe the regular compounds those complete hobby experimenter's chemical sets used to have many years ago, could be good, not the lean kits available of today. Cannot really answer the question properly, any suggestions or options would be fine. It may be something similar to fluoresceine, used to trace underground aquifers and their surfacing points; and believe fish and plants are not harmed from it. From the little I remember, it was a liquid as a result of some simple process of mixing a few chemicals. Miguel

Hello. As a kid in the sixties I read on a chemistry and physics experimenter's book written for young readers, a simple process to home make something like what is now named rhodamine, capable of dying a whole pool water red with a few drops. Cannot find it now... Does anyone know how to make such a highly concentrated dye/ink/colorant with simple compounds ? Sort of remembering borax as one ingredient, but not sure after 45 years. Oh, those days with no television, no internet... and plenty of good books to discover ! Thanks, Miguel