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Varnishing my secondary.

This weekend I managed to finish winding the secondary of my smal Tesla
coil (just over 600 turns) and now I need to varnish it. I am 14 and
don't have a budget allowing for enough varnish to just dip a coil in.
I am wondering if I could buy a small bottle of varnish and paint it
on.
 
R

Ross Marchant

Jan 1, 1970
0
This weekend I managed to finish winding the secondary of my smal Tesla
coil (just over 600 turns) and now I need to varnish it. I am 14 and
don't have a budget allowing for enough varnish to just dip a coil in.
I am wondering if I could buy a small bottle of varnish and paint it
on.

For a second I thought you said "vanishing my secretary"...
 
J

John Popelish

Jan 1, 1970
0
This weekend I managed to finish winding the secondary of my smal Tesla
coil (just over 600 turns) and now I need to varnish it. I am 14 and
don't have a budget allowing for enough varnish to just dip a coil in.
I am wondering if I could buy a small bottle of varnish and paint it
on.

I don't see why not. You should test your varnish on some extra wire
and coil form material, to make sure it dried on it, without attacking
the wire insulation (swelling, wrinkling, coming lose, etc) or the
form material before you risk doing the winding. If you can rig up
something like a hand turned lathe and have someone else slowly roll
the coil over as you run a brush along it, it should turn out nice and
smooth. The first coat (and possibly the only coat) should just
saturate the wire, excluding air from under it, if possible. Applying
varnish with it turning very slowly lets the varnish soak in, while
the air gets pushed out. Once there is varnish all around a turn, the
remaining air tends to get trapped. Fast drying varnish is not better
than slow drying. It just gives the air less time to escape and you
less time to get it smooth. I think I would try a urethane based
varnish, first, maybe thinned a bit with mineral spirits (to help it
get under the wire). If it dries very thin, you can always add
another coat of the full bodied varnish.
 
P

Pooh Bear

Jan 1, 1970
0
This weekend I managed to finish winding the secondary of my smal Tesla
coil (just over 600 turns) and now I need to varnish it. I am 14 and
don't have a budget allowing for enough varnish to just dip a coil in.
I am wondering if I could buy a small bottle of varnish and paint it
on.

Does it actually *need* varnishing ? It may be a convenient way to ensure
it's mechanical stable of course.

Graham
 
M

Mark Fergerson

Jan 1, 1970
0
Pooh said:

Dipping is not a good idea because you wind up with poor
penetration (air bubbles) and uneven coverage.

Sure, that's a time-tested method.
Does it actually *need* varnishing ? It may be a convenient way to ensure
it's mechanical stable of course.

Yes, it probably does, and not just to tie the windings down. Air
is a Bad Thing to immerse TC secondaries in because it permits
corona formation which encourages primary/secondary arcs. Of course
this depends on what voltages the thing can produce, but better safe
than sorry. Don't forget some way to hold the wire in place while
varnishing; if nothing else drill small holes near the ends and tie
the wires there, afterward fill the holes with something as similar
to the form material as possible.

A slow-drying polyurethane is best (after corona dope, but that's
more costly and I don't think a 14-yr-old can buy it as it's
basically just clear polystyrene dissolved in toluene) so as to
allow any entrapped air to escape before the stuff dries.

DO NOT shake or stir it vigorously before application because
that'll encourage air bubbles. Also saturate the brush well for the
same reason, and brush strokes should go along the "grain" of the
windings (hence the suggested lathe trick). BTW, some say that it's
best to paint the form and wind while it's drying followed with a
finish coat; you might want to try that with your next coil.

I've never seen polyurethane varnish in "small bottles", but
rather in cans (you don't want to look like a dummy at the hardware
store, do you?) and a fairly small can should allow you to apply a
couple of coats and have enough left over for other projects.


Mark L. Fergerson
 
G

Genome

Jan 1, 1970
0
This weekend I managed to finish winding the secondary of my smal Tesla
coil (just over 600 turns) and now I need to varnish it. I am 14 and
don't have a budget allowing for enough varnish to just dip a coil in.
I am wondering if I could buy a small bottle of varnish and paint it
on.

Mum might be your GirlFreud.

Have a look in the extremely large area where she keeps her 'make me look
good stuff' for something called nail varnish.

Mind you, if you're 14 then your Mum probably has some sick looking nail
varnish with bits in it.

DNA
 
A

Adrian Tuddenham

Jan 1, 1970
0
This weekend I managed to finish winding the secondary of my smal Tesla
coil (just over 600 turns) and now I need to varnish it. I am 14 and
don't have a budget allowing for enough varnish to just dip a coil in.
I am wondering if I could buy a small bottle of varnish and paint it
on.

You might want to consider the alternative method described below - but
I suggest you discuss it first with the adult who will be responsible
for helping you to clear it up if it goes wrong.


If you can get hold of a thickish plastic bag without any holes, you
could put the coil into it and add as much varnish as you can spare.
Then seal it and by squeezing and tumbling it gently, you could spread
the varnish all over the inside and outside of the coil. It may take
some time to ensure that every part has been thoroughly soaked, but you
are in no hurry because the varnish cannot begin to dry and thicken
whilst it is sealed inside the bag.

The tricky part will be removing the coil and hanging it up to drain and
dry without getting everything smothered in varnish. Perhaps you can
drill a small hole somewhere in it that doesn't matter, then you will be
able to hook it out with a loop of stiff wire through the hole. Arrange
a nail or hook to hang it from as it dries, with something underneath it
to catch the drips.

A serious problem will arise if you have any sharp edges or solder
spikes which puncture the bag. As it is a Tesla coil, you ought to have
carefully removed those at the outset.

Plan ahead and assume something (perhaps everything) will go wrong. Do
the job outdoors, keep an old washing-up bowl or bucket handy to catch
spillage, have some rags and white spirit solvent nearby for cleaning
up, wear old clothes and shoes.
 
J

John Larkin

Jan 1, 1970
0
This weekend I managed to finish winding the secondary of my smal Tesla
coil (just over 600 turns) and now I need to varnish it. I am 14 and
don't have a budget allowing for enough varnish to just dip a coil in.
I am wondering if I could buy a small bottle of varnish and paint it
on.

I originally read that as "varnishing my secretary" which seemed a bit
kinky.

Regular polyurethene varnish, sprayed or brushed a coat or two, should
be fine for tesla coils or administrative assistants.

John
 
I originally read that as "varnishing my secretary" which seemed a bit
kinky.

Regular polyurethene varnish, sprayed or brushed a coat or two, should
be fine for tesla coils or administrative assistants.

John

My first impression of "varnishing my secondary" put me in mind of
something like "waxing my weasel". Coffee in the keyboard stuff.

Jim
 
C

Clifford Heath

Jan 1, 1970
0
Mark said:
A slow-drying polyurethane is best (after corona dope, but that's more
costly and I don't think a 14-yr-old can buy it as it's basically just
clear polystyrene dissolved in toluene)

Here, I suspect even a 14-yo can buy toluene at a tiling suppliers,
as it's commonly used to clean up tile cement. Put some in a big
jar and feed as much polystyrene as you see fit - it's amazing how
much polystyrene foam you can dissolve into a given jar. If you
can't get toluene, kerosene works just as well, but will take longer
to dry.

In either case, make sure you are outdoors in a drafty area with
nothing electric operating nearby!
 
M

Mark Fergerson

Jan 1, 1970
0
Clifford said:
Mark Fergerson wrote:
Here, I suspect even a 14-yo can buy toluene at a tiling suppliers,
as it's commonly used to clean up tile cement.

Where's "here"? In AZ USA (and most other parts of the USA)
toluene got a bad rep as the solvent in model cement that produces
the "buzz" so many kids killed brain cells with. Me, I couldn't
stand the odor so I worked with open windows and a fan going.
Put some in a big
jar and feed as much polystyrene as you see fit - it's amazing how
much polystyrene foam you can dissolve into a given jar. If you
can't get toluene, kerosene works just as well, but will take longer
to dry.

Yup. I'd be careful with poly foam though. I spec'd clear
polystyrene because using the clear solid sprue (from model car
parts trees AKA sprues) pretty much guaranteed there were no
conductive inclusions, which is important when making your own
corona dope. I know this from the days I was transitioning from
building model cars to doing electronics, and wanted to put all
those saved sprues to good use. Dope made from the sprues that
windshields came off had much better holdoff than say black car body
parts; the black was probably carbon black.

I understand that nowadays in model kits polystyrene has given
way to some kind of resin which probably won't work at all, so
perhaps say pure white (no potentially conductive colorants) packing
peanuts are a decent alternative source of poly.
sigh< One of my favorite childhood hobbies is obsolete. I'm
getting old.
In either case, make sure you are outdoors in a drafty area with
nothing electric operating nearby!

Absolutely, and obviously stay the hell away from open flames,
small kids, pets, etc.


Mark L. Fergerson
 
C

Clifford Heath

Jan 1, 1970
0
Mark said:
Where's "here"?

Australia. I suspect toluene has been removed from model aircraft
dope here also, the only place I know it's used is in tiling.
Yup. I'd be careful with poly foam though.

If it's plain white, I doubt there's anything conductive in it.
I wouldn't go with peanuts, just break up the moldings from your
last monitor, TV or other household appliance. Certainly it seems
to generate enough static electricity.
 
I

Ian Stirling

Jan 1, 1970
0
This weekend I managed to finish winding the secondary of my smal Tesla
coil (just over 600 turns) and now I need to varnish it. I am 14 and
don't have a budget allowing for enough varnish to just dip a coil in.
I am wondering if I could buy a small bottle of varnish and paint it
on.

Alternatively.
It is possible to simply immerse the secondary in oil.
 
M

Mike

Jan 1, 1970
0
Mark Fergerson said:
perhaps say pure white (no potentially conductive colorants) packing
peanuts are a decent alternative source of poly.

Watch out for the ones made out of edible(ish) corn products. They
don't contain much polystyrene. If they dissolve in water, they're not
polystyrene :)
 
I

Ian Stirling

Jan 1, 1970
0
Mike said:
Watch out for the ones made out of edible(ish) corn products. They
don't contain much polystyrene. If they dissolve in water, they're not
polystyrene :)

Or if they look just like popcorn...
(got a computer packed in popcorn once. Mother started eating it.)
 
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