Question for the Materials Science Experts

[Philips210]

Hello again.

I have been finding it difficult locating a supply of bi-colour solid core hook up wire for equipment wiring so have been experimenting making some.
For a quick test, I used a PCB holder with its clamps removed. A length of plain colour solid core wire is then passed through the ends of the holder. A few Form C washers are slipped over the ends of the wire with a bulldog clip fitted over each end to hold it securely in place. The wire can thus be rotated by turning either bulldog clip. A suitable hand rest on the work surface helps to keep the paint brush steady. A series of spaced out painted bands along the wire gives the required effect. Please see a few attached pics of my first effort.

As a test, I thought I'd try Humbrol enamel model paints as I have quite a few from my model building days. I've always found this enamel paint to be very good for many applications but now, finally to my questions for the experts:

I realise oil based paint in contact with PVC wiring is probably not the best combination. Is there likely to be an adverse reaction and could it be harmful/toxic? Also, is the PVC insulation likely to be affected?

I found that dyes are used for such marking but I didn't really want to incur too much expense hence the idea of using oil based enamel paint.

Also, has anyone else experimented with marking wires with paints?

Regards,
Symon

[Roger Ramjet]

Hi Symon,

Telephone internal cabling is bi coloured but assume gauge is too small for hook up purposes ?

Rog

[Bazz4CQJ]

You need to find out what solvents are used in the Humbrol enamel (see the safety data sheet (SDS)) and then check to see if PVC is compatible with them.

I think those paints are thinned with white spirts rather than strong solvents like xylene, so I think you might be OK.

B

[paulsherwin]

I wouldn't expect there to be anything nasty in Humbrol model paints given that the primary market was children making Airfix kits.

[GrimJosef]

The trade-off when it comes to colouring the surface of polymers is between the chemistry being gentle enough not to compromise the polymer's properties versus being strong enough to make the colour stick, especially if the polymer is flexed.

The beauty of dyeing at the polymerisation or molten stage, which I assume is how mass-produced banded insulation is made, is that the colour goes deep into the PVC and so won't be prone to flaking or chipping away.

Cheers,

GJ

[Craig Sawyers]

The bicolour and tricolour wires used by Tektronix and probably HP were manufactured in house. They would buy plain colour insulated wire, and had a process for applying multicolour stripes. For certain Tektronix used to spiral the stripes so you could read them even under most circumstances.

The neatest coding from Tektronix was for the power supply lines. Attached. They used different base colour wire to determine positive or negative regulated, or unregulated.

Craig

[Radio Wrangler]

Originally Posted by Craig Sawyers

The bicolour and tricolour wires used by Tektronix and probably HP were manufactured in house. They would buy plain colour insulated wire, and had a process for applying multicolour stripes. For certain Tektronix used to spiral the stripes so you could read them even under most circumstances.

Indeed we did.The stripes were lengthwise, but spiralled gently. There were up to three stripes applied. The plain white wire ran through the machine vertically upwards. One two or three wheels of different widths rolled against the wire each applying its intended colour. Transfer wheels brought dye from tanks to wet the surface of the wheel running on the wire. The whole assemblage of wheels and tanks rotated to make the stripes spiral.

Quite hypnotising to watch in action.

There was an overall smell of solvent rather like permanent marker pens. These might be good for DIY cable marking.

The resistor colour code versus numbers was used. and reading progressively thinner stripes gave a 2,3, or 4 digit wire number.

THe first digit was normally 9 as the unstriped base colour dominated the width of any stripe, then you read the stripes in decreasing width order. So you might arrive at a code like "934" a white wire with orange and then yellow stripes. And if you look in the manual, you'll see that wire in diagrams marked 934.

David

[Ed_Dinning]

At one company where I was their chief engineer we purchased mainly white wire and built our own striping machine using permanent magic markers, so we wound up with gently spiraling strips that were quite broad. It worked well for us and when volumes increased we purchased a commercial machine

Ed

[Philips210]

Originally Posted by Roger Ramjet

Hi Symon,

Telephone internal cabling is bi coloured but assume gauge is too small for hook up purposes ?

Rog

Hello Roger.

That's a good tip thanks and would be useful for normal signal cabling.

Regards,
Symon

[Philips210]

Originally Posted by Bazz4CQJ

You need to find out what solvents are used in the Humbrol enamel (see the safety data sheet (SDS)) and then check to see if PVC is compatible with them.

I think those paints are thinned with white spirts rather than strong solvents like xylene, so I think you might be OK.

B

Bazz,

I've downloaded the Humbrol enamel paint data sheet and it would appear the solvents aren't too powerful. The ingredients are listed as: Hydrocarbons, C9-C11, n alkanes, isoalkanes, cyclics, <2% aromatics and Cobalt 6%.

There aren't any known adverse reactions with normal use so I guess it should be safe as banding on PVC. Please see attached datasheet:

Regards,
Symon

[Philips210]

Originally Posted by paulsherwin

I wouldn't expect there to be anything nasty in Humbrol model paints given that the primary market was children making Airfix kits.

Yes, Paul, that's what I would have thought. Regarding oil paint on PVC, in many older homes with surface wiring, it was often painted over without any obvious problem so for my application it ought to be fine.

Regards,
Symon

[Philips210]

Hello Craig and David.

It's good to know how the professionals made their own custom wiring and would be an interesting project to build a small machine for this. I always wondered how they produced spiralled insulation wire.

The marker pen idea is worth a try. I have a few Magic Marker dual tip pens so will look into that.

Regards,
Symon

[Philips210]

Originally Posted by GrimJosef

The trade-off when it comes to colouring the surface of polymers is between the chemistry being gentle enough not to compromise the polymer's properties versus being strong enough to make the colour stick, especially if the polymer is flexed.

The beauty of dyeing at the polymerisation or molten stage, which I assume is how mass-produced banded insulation is made, is that the colour goes deep into the PVC and so won't be prone to flaking or chipping away.

Cheers,

GJ

Hello GJ

Yes, a good point. I wouldn't expect paint to be as effective as dyes but the Humbrol paints do go on well and hold fast even with a moderate amount of flexing so the overall durability is good. My main concerns were about safety and any potential damage to the PVC. It would seem these paints will be fine for one-off construction use. I can't envisage any issues with the paint flaking off though time will tell.

Regards,
Symon

[Philips210]

Originally Posted by Ed_Dinning

At one company where I was their chief engineer we purchased mainly white wire and built our own striping machine using permanent magic markers, so we wound up with gently spiraling strips that were quite broad. It worked well for us and when volumes increased we purchased a commercial machine

Ed

Hello Ed,

I'll give my dual tip Magic Marker pens a try and see how well they adhere. I wonder if they're a similar composition to the ones in your set up?

Regards,
Symon

[Ed_Dinning]

Hi Symon, this was 45 years ago, so paint/ink compositions may have varied a bit over time.
A further thought, resistor manufacturers use an ink pen rather like the ones on chart recorders to stripe the resistors on the production line.

Ed

[Craig Sawyers]

Rapid do a range of wires with a stripe. For example https://www.rapidonline.com/rapid-eq...k-100m-01-2342

Craig

[paulsherwin]

Originally Posted by Philips210

That's a good tip thanks and would be useful for normal signal cabling.

I use it a lot for building things or doing breadboard lashups. A one metre offcut will give you 4 or 8 differently coloured solid cored wires, though the colours and diameter don't look right in vintage equipment. You'll often find lengths in builders' skips.

[Ed_Dinning]

If still available from demolition the Reddifision wired sound cables have 8 cores, 4 colours of about a 24SWG ? copper wire.
A great source of hookup wire during the mass demolition of old properties in my home town many years ago

Ed