water-based glue

[simonbaker]

This would require risking a coil, but I'd like to know the answer.

Is water-based glue bad for gluing/binding a coil?

I used it once and it seemed like the coil was less effective after gluing -- but I don't trust my setup. Many other things could have gone wrong also.

I would like to confirm whether this is a myth or not.

Ultimately I'd like to find techniques that avoid harsh chemicals to work with if possible. Lacquers, varnishes, urathanes, etc. give off fairly powerful chemicals. I'm still planning to use resin for potting/housing the coil, but it would be interesting to find some benign substance instead of that too.

-SB

[dfbowers]

This would require risking a coil, but I'd like to know the answer.

Is water-based glue bad for gluing/binding a coil?

I used it once and it seemed like the coil was less effective after gluing -- but I don't trust my setup. Many other things could have gone wrong also.

I would like to confirm whether this is a myth or not.

Ultimately I'd like to find techniques that avoid harsh chemicals to work with if possible. Lacquers, varnishes, urathanes, etc. give off fairly powerful chemicals. I'm still planning to use resin for potting/housing the coil, but it would be interesting to find some benign substance instead of that too.

-SB

Simon,

I can give it a try just to see if I have the same experience with coils becoming less effective. The only drawback I would see would be shrinkage, setting time and maybe conductive. For me, hot glue seems to be a quick way to set coils in shells first, but it must be from a HOT glue gun as some are low or medium heat and don't stick too well.

I can see the concern for epoxy as it's not the most people friendly stuff. I have used it but only under an exhaust hood or outside as I have heard horror stories about people suddenly developing bad allergic reactions. Not to mention, it's impossible to clean up off the wife's carpet!

[simonbaker]

Simon,

I can give it a try just to see if I have the same experience with coils becoming less effective. The only drawback I would see would be shrinkage, setting time and maybe conductive. For me, hot glue seems to be a quick way to set coils in shells first, but it must be from a HOT glue gun as some are low or medium heat and don't stick too well.

I can see the concern for epoxy as it's not the most people friendly stuff. I have used it but only under an exhaust hood or outside as I have heard horror stories about people suddenly developing bad allergic reactions. Not to mention, it's impossible to clean up off the wife's carpet!

I'd be interested in what you find. Now, what is the best glue to try? I was gung-ho on Elmers because of convenience and safety, but looking at a glue job a year later I didn't like what I saw -- seemed to shrink or break up kind of. But I was using it for two purposes -- to bind together the coil windings (like your varnish), and to attach coil to form (piece of wood). Maybe the windings are OK -- the attachment didn't seem so good.

So for just binding, there might be some friendly sticky stuff. Not sure how important it is to maintain long-term solidity since it is all taped and potted, but instinctively I feel that maybe it is important for vibrations -- in that case I would hesitate to use the water-based glue unless proven.

As for conductivity -- in some ways, it could be a benefit, sort of like those painted shields. But I wondered if rather than conductivity, there was a problem with trapped water dipoles doing something. Pure conjecture. But there seemed to be a dramatic effect on my coil; again, possibly due to something else.

I may actually try egg whites -- they make a surprisingly good and long-lasting glue, like a varnish even. And finally can make use of those chickens in my Faraday cage...

May seem like a dumb topic, but I like to think in terms of MD building for hobbiests, like for your and Dennis the Mennis book (something I had also aspired to produce in some form or other) ...

-SB

[pebe]

How about using bog-standard satin emulsion paint? Once dried, it's difficult to get spillages off anything so it should make a good adhesive for the windings.

[dfbowers]

I'd be interested in what you find. Now, what is the best glue to try? I was gung-ho on Elmers because of convenience and safety, but looking at a glue job a year later I didn't like what I saw -- seemed to shrink or break up kind of. But I was using it for two purposes -- to bind together the coil windings (like your varnish), and to attach coil to form (piece of wood). Maybe the windings are OK -- the attachment didn't seem so good.

So for just binding, there might be some friendly sticky stuff. Not sure how important it is to maintain long-term solidity since it is all taped and potted, but instinctively I feel that maybe it is important for vibrations -- in that case I would hesitate to use the water-based glue unless proven.

As for conductivity -- in some ways, it could be a benefit, sort of like those painted shields. But I wondered if rather than conductivity, there was a problem with trapped water dipoles doing something. Pure conjecture. But there seemed to be a dramatic effect on my coil; again, possibly due to something else.

I may actually try egg whites -- they make a surprisingly good and long-lasting glue, like a varnish even. And finally can make use of those chickens in my Faraday cage...

May seem like a dumb topic, but I like to think in terms of MD building for hobbiests, like for your and Dennis the Mennis book (something I had also aspired to produce in some form or other) ...

-SB

Egg whites.. now there's a thought! My dad taught me to make kites when I was little but using flower and eggs for glue.. It did work.

Maybe if we try water based glue it should have a gap in it somewhere, just like a shield? (just speculation). That way, even if it were conductive it would not matter.I will give it a try tonight when I get home.

Another thought would be contact cement. Somehow coat the wires before it goes on the form and it "sticks" even after drying.

[simonbaker]

Egg whites.. now there's a thought! My dad taught me to make kites when I was little but using flower and eggs for glue.. It did work.

Maybe if we try water based glue it should have a gap in it somewhere, just like a shield? (just speculation). That way, even if it were conductive it would not matter.I will give it a try tonight when I get home.

Another thought would be contact cement. Somehow coat the wires before it goes on the form and it "sticks" even after drying.

I always remember a little patch of egg white on my desk (after some experiment I did) that lasted years and years like plexiglass. Made an impression on me.

Yes -- tacky glue (contact cement) probably would work. It resembles Elmers glue but gummier. Actually Elmers works pretty well as adhesive to bind coil (takes a little while to dry though), but not sure if it skunks the coil electronics somehow or if it holds up over time. But those eventually dry hard, maybe you mean a permanently sticky agent which could be another approach -- like silicone rubber. I read that U of Oregon is inventing a sticky glue made from vegetable oil.

I remember there was a LePages paper glue that had a kind of varnishy finish to it -- but probably would turn to dust over time.

Hard to beat the good ol' toxic formulas.

I have a feeling the conductivity of these water-based glues when dry is so low that they have no chance of working like shields anyway -- generally you have to dump loads of graphite in I think. And I think once the resistance gets over a few thousand ohms the need for a gap disappears because the current really is tiny. But they perhaps still could do something funny to the mag field, just don't know.

On another note, I definitely would like to experiment with a quasi-conductive potting material, like graphite-epoxy or graphite-resin mix, to eliminate the foil shield.

-SB

[dfbowers]

I always remember a little patch of egg white on my desk (after some experiment I did) that lasted years and years like plexiglass. Made an impression on me.

Yes -- tacky glue (contact cement) probably would work. It resembles Elmers glue but gummier. Actually Elmers works pretty well as adhesive to bind coil (takes a little while to dry though), but not sure if it skunks the coil electronics somehow or if it holds up over time. But those eventually dry hard, maybe you mean a permanently sticky agent which could be another approach -- like silicone rubber. I read that U of Oregon is inventing a sticky glue made from vegetable oil.

I remember there was a LePages paper glue that had a kind of varnishy finish to it -- but probably would turn to dust over time.

Hard to beat the good ol' toxic formulas.

I have a feeling the conductivity of these water-based glues when dry is so low that they have no chance of working like shields anyway -- generally you have to dump loads of graphite in I think. And I think once the resistance gets over a few thousand ohms the need for a gap disappears because the current really is tiny. But they perhaps still could do something funny to the mag field, just don't know.

On another note, I definitely would like to experiment with a quasi-conductive potting material, like graphite-epoxy or graphite-resin mix, to eliminate the foil shield.

-SB

Hmmm.. I could probably try that too. I have a few carbon rods laying around. I ground one up a while ago and I was going to use it as filler material but when I discovered that it was conductive I threw it out!!.. I forgot that Tesoro uses a similar method for shielding.

[simonbaker]

How about using bog-standard satin emulsion paint? Once dried, it's difficult to get spillages off anything so it should make a good adhesive for the windings.

That could be good too. Maybe give it a try.

I've got to find a better "applicator" pot for my sticky-wire -- if my pot of glue dries up I have to engineer an new one. It has a hook that holds the wire under the glue.

Minimal mess is a real goal because winding coils gets gnarly by itself.

-SB

[J_Player]

Here are some thoughts I had about potting materials:

Water based glues:
Water based glues, paints and egg whites become hard when the water evaporates from the glue mixture. If it is used as a potting material, it may take some time for the center of the glued area to become completely dry. The drying time could be accelerated by placing the potted coil in a warm area for a long time until you feel it is fully dried. Of course, we can expect the conductivity of this material to be greater if it has some moisture content. And the conductivity may vary if the moisture is not constant throughout the core of the potted coil. Another concern is water based glue (Elmer's white glue, or egg whites) are not waterproof. So if some water gets behind the outer coil enclosure to the potting material, it may dissolve the glue and return it to its liquid state. Also, expect this material to shrink as it dries. If it gets wet for a long time, it will begin to swell up again as it becomes more watery.

Oil based adhesives and paints:
The oil based adhesives and paints work similar to water based, except volatile spirits evaporate from the material which were originally added to keep the material as a thin low viscosity liquid that can be poured or brushed on. In the process of drying, these materials develop microscopic worm holes which allow the gasses to excape while the volatile materials are evaporating. They may dry as a rather solid potting material, but inspection under a powerful microscope will reveal they have tiny pours which penetrate into the interior of the material.

Epoxies and 2-part Urethanes:
Epoxies, 2-part urethanes, and 2-part polyester/vinylester resins can be used without volatile thinners that evaporate. As an example, a pure 2-part epoxy formulated to set in 4 hours or longer does not become hard by using the process of evaporating volatiles which were designed to keep it thin. It becomes hard through a chemical reaction which forms chemical bonds in the material that convert it from a liquid material to a hard material. Some epoxies are actually made hard without the addition of a second material, and will set by simply heating them to a given temperature until the chemical reaction begins which causes them to harden. The result is they become hard without giving off a large amount of volatile vapors that leave microscopic worm holes that penetrate the surface. The allergic reactions are real for sensitive people. These are usually caused by the catalyst that is added to the resin which invariably gets into the air. Epoxies should be used in well ventilated areas to avoid any chance of inhaling fumes that could cause allergic reactions. Be sure to wear gloves so it doesn't get on your skin. Also, it is important to use the correct ratio of catalyst to resin. This is best done by weight with an accurate scale. If you use too much catalyst, then you will have an excess which can continue to cause allergic reactions even after it becomes hard. But generally speaking epoxies, polyesters, and vinylester resins are fairly safe if applied properly. We see evidence of their safety in the thousands of surfboards and boat surfaces that are finished with these resins, and don't cause problems for the people who use them. The epoxies are considered very good for preventing moisture intrusion, and have excellent strength especially when combined with a composite material.

Semi-rigid materials:
There are a number of inexpensive materials that can be used to pot a coil. The two that come to mind are polyurethane caulk and silicon caulk. These can be bought at Home Depot for under $5/tube that will make 2 or more coils. These caulks also dry without relying on evaporating any water or volatile materials. The dried caulking is semi-rigid and waterproof, as you have seen used to hold the corner seams of aquariums. My personal choice would be polyurethane caulk, because it does not have the brittle tendency of silicon. That is to say, if you nick the surface with a knife, silicon is more likely to have the cut continue to grow deeper than you cut it than urethane caulk. Home Depot sells PL brand polyurethane caulk for around $4 per tube in several colors. When working with either silicon or urethane caulks, you will have a hard time removing any wet spills. You can clean up with lacquer thinner. Another tip is you can smooth the surface of the caulk by wetting your finger and wiping it across the surface. If you find any of it begins to stick to your finger, then wipe your finger clean with a tissue and wet it again to finish the job of smoothing the surface.

You can also get a semi-rigid potting material by sending to the companies that produce theatrical prosthetics (rubberized skin that can be formed to create new faces), and from model making suppliers. These companies sell latex based prosthetics which ultimately will have tiny pours in them, and are fairly elastic. The model-makers materials are usually 2-part urethane that can be ordered with various elastic properties from nearly rigid, to rubber-band consistency. These do not form micro pours. They are expensive, but they are often used as molds to cast plaster or resin items with fine details.

A final word about rubber cement and contact cement:
Rubber cement and contact cement are actually polyurethane with volatile solvents added to keep them liquid. They work by allowing the solvents to evaporate, which causes them to become the hardness that they were formulated to be. (This hardness is similar to an eraser on a pencil). There are water based versions which work the same way.

So now you know what I know about potting materials. What I don't know is the electrical properties of these materials. I presume all of them are suitable insulators except maybe the water based materials which could have various conductivity at different parts of the potted coil. I would expect that I would need to add a faraday shield over whatever material I used to pot the coil.

If I had to choose, I would start with a tube of urethane caulk, or maybe a 2 part epoxy.

Best wishes,
J_P

[Carl-NC]

I forgot that Tesoro uses a similar method for shielding.

They do? I once opened a Tesoro coil, and the shield was brush-painted on. It appeared they first shield-painted the plastic shell, placed all the coils etc in, and did a 1st epoxy pour. When that hardened, they shield-painted the poured epoxy, then did a 2nd pour of finish epoxy. None of the epoxy appeared to be conductive.

- Carl

[dfbowers]

They do? I once opened a Tesoro coil, and the shield was brush-painted on. It appeared they first shield-painted the plastic shell, placed all the coils etc in, and did a 1st epoxy pour. When that hardened, they shield-painted the poured epoxy, then did a 2nd pour of finish epoxy. None of the epoxy appeared to be conductive.

- Carl

Hey Carl,

I do not have first hand knowedge of this. It's pure speculation based on what is published at a few websites describing the newer Tesoro coils:

"The 12x10 widescan is designed to penetrate deeply in highly mineralized sites that are not burdened with an abundance of junk. The Double D windings “see” 70% less ground effect than a concentric-style winding. This will give you smoother operation in areas where the ground matrix tends to shift. This coil will utilize our Monolithic shielding. Carbon fibers and graphite powder have been mixed into the raw plastic used to form the coils. This technique provides an even RF shielding across the entire surface of the coil
"

Just trying to figure out what they are doing..

Don

[ZTDMP]

http://www.md4u.ru/forum/viewtopic.php?p=62403#p62403

[dfbowers]

Here are some thoughts I had about potting materials:

Water based glues:
Water based glues, paints and egg whites become hard when the water evaporates from the glue mixture. If it is used as a potting material, it may take some time for the center of the glued area to become completely dry. The drying time could be accelerated by placing the potted coil in a warm area for a long time until you feel it is fully dried. Of course, we can expect the conductivity of this material to be greater if it has some moisture content. And the conductivity may vary if the moisture is not constant throughout the core of the potted coil. Another concern is water based glue (Elmer's white glue, or egg whites) are not waterproof. So if some water gets behind the outer coil enclosure to the potting material, it may dissolve the glue and return it to its liquid state. Also, expect this material to shrink as it dries. If it gets wet for a long time, it will begin to swell up again as it becomes more watery.

Oil based adhesives and paints:
The oil based adhesives and paints work similar to water based, except volatile spirits evaporate from the material which were originally added to keep the material as a thin low viscosity liquid that can be poured or brushed on. In the process of drying, these materials develop microscopic worm holes which allow the gasses to excape while the volatile materials are evaporating. They may dry as a rather solid potting material, but inspection under a powerful microscope will reveal they have tiny pours which penetrate into the interior of the material.

Epoxies and 2-part Urethanes:
Epoxies, 2-part urethanes, and 2-part polyester/vinylester resins can be used without volatile thinners that evaporate. As an example, a pure 2-part epoxy formulated to set in 4 hours or longer does not become hard by using the process of evaporating volatiles which were designed to keep it thin. It becomes hard through a chemical reaction which forms chemical bonds in the material that convert it from a liquid material to a hard material. Some epoxies are actually made hard without the addition of a second material, and will set by simply heating them to a given temperature until the chemical reaction begins which causes them to harden. The result is they become hard without giving off a large amount of volatile vapors that leave microscopic worm holes that penetrate the surface. The allergic reactions are real for sensitive people. These are usually caused by the catalyst that is added to the resin which invariably gets into the air. Epoxies should be used in well ventilated areas to avoid any chance of inhaling fumes that could cause allergic reactions. Be sure to wear gloves so it doesn't get on your skin. Also, it is important to use the correct ratio of catalyst to resin. This is best done by weight with an accurate scale. If you use too much catalyst, then you will have an excess which can continue to cause allergic reactions even after it becomes hard. But generally speaking epoxies, polyesters, and vinylester resins are fairly safe if applied properly. We see evidence of their safety in the thousands of surfboards and boat surfaces that are finished with these resins, and don't cause problems for the people who use them. The epoxies are considered very good for preventing moisture intrusion, and have excellent strength especially when combined with a composite material.

Semi-rigid materials:
There are a number of inexpensive materials that can be used to pot a coil. The two that come to mind are polyurethane caulk and silicon caulk. These can be bought at Home Depot for under $5/tube that will make 2 or more coils. These caulks also dry without relying on evaporating any water or volatile materials. The dried caulking is semi-rigid and waterproof, as you have seen used to hold the corner seams of aquariums. My personal choice would be polyurethane caulk, because it does not have the brittle tendency of silicon. That is to say, if you nick the surface with a knife, silicon is more likely to have the cut continue to grow deeper than you cut it than urethane caulk. Home Depot sells PL brand polyurethane caulk for around $4 per tube in several colors. When working with either silicon or urethane caulks, you will have a hard time removing any wet spills. You can clean up with lacquer thinner. Another tip is you can smooth the surface of the caulk by wetting your finger and wiping it across the surface. If you find any of it begins to stick to your finger, then wipe your finger clean with a tissue and wet it again to finish the job of smoothing the surface.

You can also get a semi-rigid potting material by sending to the companies that produce theatrical prosthetics (rubberized skin that can be formed to create new faces), and from model making suppliers. These companies sell latex based prosthetics which ultimately will have tiny pours in them, and are fairly elastic. The model-makers materials are usually 2-part urethane that can be ordered with various elastic properties from nearly rigid, to rubber-band consistency. These do not form micro pours. They are expensive, but they are often used as molds to cast plaster or resin items with fine details.

A final word about rubber cement and contact cement:
Rubber cement and contact cement are actually polyurethane with volatile solvents added to keep them liquid. They work by allowing the solvents to evaporate, which causes them to become the hardness that they were formulated to be. (This hardness is similar to an eraser on a pencil). There are water based versions which work the same way.

So now you know what I know about potting materials. What I don't know is the electrical properties of these materials. I presume all of them are suitable insulators except maybe the water based materials which could have various conductivity at different parts of the potted coil. I would expect that I would need to add a faraday shield over whatever material I used to pot the coil.

If I had to choose, I would start with a tube of urethane caulk, or maybe a 2 part epoxy.

Best wishes,
J_P

Well after a few IB coil failures, I would stay away from Semi -Rigid potting compounds. I would select something that is Hard, light and has no shrinkage when curing. Even some epoxies will not fit the bill!!

I will put some numbers to it. The only compound that I have tried so far that has worked perfectly is "MG Chemicals 832B-375ML". That's not to say that many others will not work, but it has a "Shore D" hardness of about 80.

Don

[simonbaker]

Well after a few IB coil failures, I would stay away from Semi -Rigid potting compounds. I would select something that is Hard, light and has no shrinkage when curing. Even some epoxies will not fit the bill!!

I will put some numbers to it. The only compound that I have tried so far that has worked perfectly is "MG Chemicals 832B-375ML". That's not to say that many others will not work, but it has a "Shore D" hardness of about 80.

Don

That's interesting because I was attracted to the caulk idea. What experiences did you have? Is there a vibration problem?

-SB

[simonbaker]

Here are some thoughts I had about potting materials:

...................
If I had to choose, I would start with a tube of urethane caulk, or maybe a 2 part epoxy.

Best wishes,
J_P

Thanks, gives a picture of how these glues work, very interesting.

How does "resin" (the kind used with fiberglass) fit into this?

-SB