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Polycore Thread
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Adam Thibault
(apthibault) - M
Polycore Thread on 11/12/2012 14:57:56 MST Print View

I know it's not ultralight but I got my canvas to start sewing my winter pyramid tent. The research I've done has indicated that the best thread for sewing canvas has a polyester core and is wrapped with cotton (something about the cotton exterior swells when wet and fills the needle hole). I'm having a difficult time finding such a thread, can anyone point me in the right direction? At one point there was a thread called Filco thread that people used to sew tipis, is it still available? BTW - I think I'm looking for size 12 thread...

Many thanks!

jerry adams
(retiredjerry) - MLife

Locale: Oregon and Washington
Re: Polycore Thread on 11/12/2012 15:31:05 MST Print View

You can find cotton covered polyester thread at the fabric store, but it's fairly light weight, probably not what you're looking for.

Tad Englund
(bestbuilder) - F - MLife

Locale: Pacific Northwest
Re: Polycore Thread on 11/12/2012 16:14:32 MST Print View

Adam, PM Roger Coffin to answer your question (post his answer to this tread).

I think he uses Taslan, but it might be 100% nylon and I haven't found it for sell in the states.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Oh, the complexity! on 11/13/2012 14:45:19 MST Print View

You would not believe just how complex this sewing thread issue can become. Seriously!

One major use for polyester-core, cotton covered (poly-cotton) thread is in high-speed stop-start machines. The high-speed bit means the thread is screaming through the eye of the needle and the needle gets hot. When the machine stops the hot needle can actually partially melt a straight polyester thread. The ensuing tangle and disaster has to be seen to be believed. The needle usually breaks and the broken end punches big holes through the fabric. $$$! But when the thread has an outer cotton layer (eg Amann Rasant) there is less friction (so less heating) and the cotton surface means the thread does not melt either. Everyone is happy. What relevance does this speed business have to home sewing? Not much.

Yes, the cotton will swell slightly when it gets wet. But the amount of swelling with a light poly-cotton thread is so small it is extremely unlikely to do anything about filling up the needle holes in my experience. However, PU and silicone sealant do stick fairly well to the cotton surface, which makes seam-sealing a bit easier.

A straight polyester thread (eg Amann Serafil) can be very smooth and strong, but it can also get fouled up in a domestic machine. The surface of the thread is not really smooth and the thread tends to get twisted as it goes through the friction device. The end results are tangles and jams in the thread before it gets to the needle. These threads can be used, but you have to know how.

For sewing packs we often use a very strong bonded nylon thread. These do not twist up the same as the 100% polyester threads (fortunately), but they are all too heavy for use on clothing or tents.

I am not all that enthused about the mass-market (Gutermann etc) threads, at least not for tents etc. But I do use those brands for Taslan (Supplex) clothing because I can get matching colurs fairly easily. Only a few shops carry the Rasant thread, and then in only a few colours in the 120 size, because the Amann brand is more for commercial use. I am not sure it has much penetration into the USA market, but then little commercial sewing is done in the USA these days.

You can also get big cheap reels of overlocker thread in local shops. This has a very slow twist. It's fine for overlockers, but the stuff can be a disaster in a conventional domestic machine. Don't even try that.


Adam Thibault
(apthibault) - M
Rasant Thread on 11/13/2012 16:22:40 MST Print View

Roger - you're incredible, thanks so much...

Quick follow-up question, it looks like I can get Rasant 120 shipped from Australia on ebay for ~$22. Would this size work in my home sewing machince (an old Necchi)? If so, do you happen to know what size of needle would work well? Would this size of thread be good to use for my canvas pyramid? Thanks again!

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Rasant Thread on 11/13/2012 19:02:01 MST Print View

Hi Adam

Yes, Amann do sell a bit in Australia.

I can use the Rasant 120 in most any machine. I use it for silnylon and netting with a #60 needle - the smallest size. Works fine.

You mention 'canvas'. To me that means a fairly heavy fabric - normally poly-cotton, maybe 8 oz or even 12 oz. I would NOT use Rasant 120 on that: it would be far too light. Rasant 75 would be better, but still a bit light. If you are getting into the genuine '8 oz/12 oz canvas' class though, either Rasant 50 or a bonded nylon thread might be better. With Rasant 75 I use a #70 needle with care or a more likely a #80 needle; with bonded nylon thread I use a #100 needle.