depends....
on the exact type of carbon black used in the ink. Some carbon black are such that the particles of carbon are actuallly coated and are then are not conductive. You only need to obtain a small sample to find out. Have fun. When people find out what you want the ink for they are usually fastinated and are almost always happy to lend a hand in the name of musical science. Regards Moray James.
on the exact type of carbon black used in the ink. Some carbon black are such that the particles of carbon are actuallly coated and are then are not conductive. You only need to obtain a small sample to find out. Have fun. When people find out what you want the ink for they are usually fastinated and are almost always happy to lend a hand in the name of musical science. Regards Moray James.
Why not use Aquadag? Its a product used for coating the back of TV picture tubes, for grounding purposes.
It was suggested as a conductive film for ESLs in an article I read years ago.
http://www.achesonindustries.com/doc/pds/Aquadag.pdf
Good luck with the project. I can never decide between ES or Ribbon. I have a lot of respect for those who roll their own, either way.
BTW, on reading this thread, I glanced at my laser printer. That fuses carbon to the paper doesn't it? No go. Reads open circuit on my digimeter.
Regards,
Geoff.
It was suggested as a conductive film for ESLs in an article I read years ago.
http://www.achesonindustries.com/doc/pds/Aquadag.pdf
Good luck with the project. I can never decide between ES or Ribbon. I have a lot of respect for those who roll their own, either way.
BTW, on reading this thread, I glanced at my laser printer. That fuses carbon to the paper doesn't it? No go. Reads open circuit on my digimeter.
Regards,
Geoff.
I_Forgot said:
I can't understand the the persisting promoting of Licron. It may be good, but not in all cases as I will explain.
I have seen it and I have measured it. A homogeneous layer is more than five times as heavy as the EC-coating. The thinnest result I could get was more than twice as thick. Now this surface looked a bit spotted but resistance still was reasonable uniform, not good. Resistance of this thinnest as possible layer wasn't higher as 100 Mohm.
Adhesion to Mylar is good, but thicker layers have tendency to crack.
Because of the milky (not transparant!) appearence, the use in open esls like audiostatic, martin logan, final is out of question.
If you use speaker grill cloth to hide the Mylar and are taking care to spray a very thin, slightly spotted, layer you will have a system which adheres well and is easy to use. Added mass is not the best, but acceptable for most amateurs. Same is for the resistance which is on the low side. So it is an option which should be seriously considered, but there are limitations.
Hi,
I have to admit to Martin´s words. I won´t use Licron any more. First its quite expensive. Than is it nearly impossible to get an even coating with this
spraycan. The appearance is milky-greyisch and not even. It dries out very quick. In fact so quick that You can´t correct for any failure. It adds considerable mass, such that You can hear a distinct difference in resolution and attack of the panel. It sounds like the difference between a 12µm and 3µm diaphragm. Its resistance is low. That will work for hybrids and small panels but probabely not very well for fullrangers.
There are other coatings that are better suited to this application.
Aquadag, EC, Hobby-glue, Pedot, which all four have proven to me to work better than licron. Especially the Hobby-glue is a good solution with respect to price, flexibility of resistance, handling, safety, transparency, longtime stability and added weight.
jauu
Calvin
I have to admit to Martin´s words. I won´t use Licron any more. First its quite expensive. Than is it nearly impossible to get an even coating with this
spraycan. The appearance is milky-greyisch and not even. It dries out very quick. In fact so quick that You can´t correct for any failure. It adds considerable mass, such that You can hear a distinct difference in resolution and attack of the panel. It sounds like the difference between a 12µm and 3µm diaphragm. Its resistance is low. That will work for hybrids and small panels but probabely not very well for fullrangers.There are other coatings that are better suited to this application.
Aquadag, EC, Hobby-glue, Pedot, which all four have proven to me to work better than licron. Especially the Hobby-glue is a good solution with respect to price, flexibility of resistance, handling, safety, transparency, longtime stability and added weight.
jauu
Calvin
Hi,
Among the HC-systems, the dissolved hobby glue is the best you can get, also very cheap. Transparent as well. So Calvin is right here.
The only disadvantage is the very high resistance in the Giga-ohm range. Depending on temperature and humidity the resistance increases and may be at the same order as the 'leakage' resistance so the charging process will be affected. This is the reason that pure hobby glue will not work as well in every esl. The same thing for methylcellulose / hypromellose
Some people are trying to lower the resistance by doping the glue with ionic substances such as stearates or small ions like ammoniumsalts. This may work, but resistance will increase over time again.
Hobby glue should be properly diluted to achieve low added mass.
Among the HC-systems, the dissolved hobby glue is the best you can get, also very cheap. Transparent as well. So Calvin is right here.
The only disadvantage is the very high resistance in the Giga-ohm range. Depending on temperature and humidity the resistance increases and may be at the same order as the 'leakage' resistance so the charging process will be affected. This is the reason that pure hobby glue will not work as well in every esl. The same thing for methylcellulose / hypromellose
Some people are trying to lower the resistance by doping the glue with ionic substances such as stearates or small ions like ammoniumsalts. This may work, but resistance will increase over time again.
Hobby glue should be properly diluted to achieve low added mass.
Hobby glue...
for the most pat they are talking about PVA (white glue) there are all kinds of brands and versions. In America you can buy Weldbond or other white glue usually sold as wood glue. If you dilute it five parts of water to one part glue you can apply it with a mister bottle in a very fine layer. You can dope it wit Quats or conductive carbon powder. You can also try our clear floor polish (diluted) which will work fine. The trick to making this stuff stick is to dilute it. You can probably dope it with just about any brand of antistatic compound. Regards Moray James.
for the most pat they are talking about PVA (white glue) there are all kinds of brands and versions. In America you can buy Weldbond or other white glue usually sold as wood glue. If you dilute it five parts of water to one part glue you can apply it with a mister bottle in a very fine layer. You can dope it wit Quats or conductive carbon powder. You can also try our clear floor polish (diluted) which will work fine. The trick to making this stuff stick is to dilute it. You can probably dope it with just about any brand of antistatic compound. Regards Moray James.
Hi,
Martin´s right about pure hobby-glue. The trick is to find the right one(!) and add some dope.
Black ink for writing pencils can be used with good success as doping material. Just add some drops of it (~2 small drops are enough for ~20mL).
Dilute with destilled, deionized water (used for car batteries).
The glue seems to destroy the surface tension of the water, so that the tendency to build up streaks of small dots when applying to the film is very low. Normally You should get a very fine and thin and even coating.
You can apply by brushing with a piece of lint free cloth or a foam brush (very thin) or with an airbrush-pistol (thicker coating). Even though the solution is greyish in apperance in a bottle, its hardly visible at all when You apply it. Only holding against light You recognize a slight rainbow-like shimmer (like a drop of gasoline on water) when it has dried. Another good point is, that You can coat the film two or more times. So if You´re recipe is too high in ohmic value, You don´t need a complete new film, but just add some more drops of black ink to Your solution and recoat again.
This solution works very stable for more than 5years now without any tendency of change yet (every now and than I get my oldest panels out of the damp, cold, open to free air cellar where they are stored, dedust and clean them, hook them up, measure and listen to them and find them still in prime condition). So I assume that the hobbyglue formula will be good for >10years of life
jauu
Calvin
Martin´s right about pure hobby-glue. The trick is to find the right one(!) and add some dope.
Black ink for writing pencils can be used with good success as doping material. Just add some drops of it (~2 small drops are enough for ~20mL).
Dilute with destilled, deionized water (used for car batteries).
The glue seems to destroy the surface tension of the water, so that the tendency to build up streaks of small dots when applying to the film is very low. Normally You should get a very fine and thin and even coating.
You can apply by brushing with a piece of lint free cloth or a foam brush (very thin) or with an airbrush-pistol (thicker coating). Even though the solution is greyish in apperance in a bottle, its hardly visible at all when You apply it. Only holding against light You recognize a slight rainbow-like shimmer (like a drop of gasoline on water) when it has dried. Another good point is, that You can coat the film two or more times. So if You´re recipe is too high in ohmic value, You don´t need a complete new film, but just add some more drops of black ink to Your solution and recoat again.
This solution works very stable for more than 5years now without any tendency of change yet (every now and than I get my oldest panels out of the damp, cold, open to free air cellar where they are stored, dedust and clean them, hook them up, measure and listen to them and find them still in prime condition). So I assume that the hobbyglue formula will be good for >10years of life
jauu
Calvin
Hi,
Hobby glue is not the white PVA stuff.
There are transparant hobby glues as well (Tesa). Doping with ink is based on the addition of small ions (salts) which makes it more hydrophylic. In a damp cellar they probably are saturated with moisture while putting them close to a heater or in sunlight removes the moisture. I recommend doping to a rather low resistance (10 Mohm), since such HC systems can increase their reistance 1000 times depending on humidity and temperature.
Hobby glue is not the white PVA stuff.
There are transparant hobby glues as well (Tesa). Doping with ink is based on the addition of small ions (salts) which makes it more hydrophylic. In a damp cellar they probably are saturated with moisture while putting them close to a heater or in sunlight removes the moisture. I recommend doping to a rather low resistance (10 Mohm), since such HC systems can increase their reistance 1000 times depending on humidity and temperature.
danielm said:
Hi,
The proper measurements of surface resistances involves a four point measuring device with controlled contact pressure. Clean probes are required to eliminate wrong measurements caused by dirt/fingerprints. For DIY a conventional multi-device with the right range will do the job as well. Cheaper as well.
A resistance of around 1 gigaohm (10 exp9) is high enough for equally distributed (fixed) charge and low enough to ensure proper charging.
Tesa is not the most reliable choice, since it can increase its resistance 1000 times. I have used it on several panels and some of them didn't charge up completely. Since the resistance is out of range of most devices it is difficult to check what you have done.
Hi,
it´s nearly impossible to measure these high resistances without the proper equipment and set-ups, but You can quite easily measure with normal DIY-equipment to estimate the approximate range of the impedance.
A Multimeter has a defined inner resistance (mostly 10megs). If You connect the meter and the diaphragm in series, this forms a voltage divider for the high voltage bias with lots of voltage over the coating and just some millivolts over the multimeter. You can now calculate the current through the circuit and hence calculate the resistance of the coating. Again- this method is not precise- it just gives You an idea about the impedance value!
jauu
Calvin
it´s nearly impossible to measure these high resistances without the proper equipment and set-ups, but You can quite easily measure with normal DIY-equipment to estimate the approximate range of the impedance.
A Multimeter has a defined inner resistance (mostly 10megs). If You connect the meter and the diaphragm in series, this forms a voltage divider for the high voltage bias with lots of voltage over the coating and just some millivolts over the multimeter. You can now calculate the current through the circuit and hence calculate the resistance of the coating. Again- this method is not precise- it just gives You an idea about the impedance value!
jauu
Calvin
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