Pam Wedd

Wood canvas canoe builder
Hi folks
Anyone out there used Nepheline Syenite instead of silica in their filler recipe?? I used it back in the early 90's and for some reason stopped - perhaps as all the recipes always called for silica. Seems like the neph sy is just another ground up rock but not chrystalline so won't give you silicosis. If it works as well as the silica, perhaps we should all be using it. Probably just not quite as hard, but maybe it would be hard to tell the difference between ground up quartz and ground up granite???
From the Canadian Encyclopedia website...

Nepheline syenite is a white to light grey medium-grained IGNEOUS ROCK. It consists mostly of soda feldspar, nepheline and potash feldspar, accessory magnesium and iron-rich minerals. The Canadian nepheline syenite industry began in 1932 when claims were staked on Blue Mountain near Peterborough, Ontario, where it is still produced. Persistent and lengthy efforts in technical and market research and development were necessary to establish this industry. Canada was the first country to develop the use of nepheline syenite as a raw material for glass, ceramic and filler industries and was the world's only producer for many years.
Over the years, nepheline syenite has become preferred to feldspar as a source of alumina and alkalis for glass manufacture. It promotes more rapid melting at lower temperatures, thus reducing energy consumption, lengthening the life of the furnace and improving the yield and quality of glass. The material is used in ceramic glazes and enamels and in fillers in paints, papers, plastics and foam rubber. In Canada, about two-thirds of nepheline syenite is consumed by the glass industry for containers, flat glass, insulating fibreglass and textile glass fibre.

Nepheline syenite is extracted from open pit mines. Ore is hauled to the mill, where it is put through a magnetic separation circuit to remove iron-bearing minerals. The mill produces several grades of nepheline syenite, based on grain size and iron content, to meet a wide variety of markets. Annual shipments exceed 700 000 t.
Nepheline Syenite

Your resident Geologist here:

Nepheline syenite is a wonderful rock! It is a plutonic rock (cooled in a chamber beneath the earth's surface) composed of mostly the minerals feldspar, nepheline, and minor ferromagnesian minerals. It is similar to a granite, but the nepheline shows up instead of the quartz found in granite. There is a big pluton of the stuff in southern Maine. Maybe Benson can mine us a bunch (Rattlesnake Mountain). Nepheline is a nice pink mineral.

I'm not sure of the avoiding of silicosis part. This rock has less silica (silica undersaturated) (no quartz), than a granite (plenty of quartz) but the minerals that make up the nepheline syenite rock feldspathoid mineral (nepheline - (Na,K)[AlSiO4]) and feldspar still contain some silica. I just don't know the real underlying causes behind silicosis - is dust the real issue or some property of silica? The minerals in nepheline syenite are crystalline. I think silicosis is mostly a crystalline dust problem and as such I don't think you can avoid it by using syenite. The particle size is also a contributing factor. Respirable dust is a big problem.

I have heard that people use garnet to sand blast because it is a heavier and denser mineral and thereby falls out of the air and creates less dust to avoid the hazards of silicosis.

I suspect you would not be able to tell the difference in hardness between a canoe filled with ground up granite, ground up quartz, or ground up syenite.
Last edited:
nepheline syenite prices

Thanks all. Not sure where we find out the medical end of this, but the neph sy is 42 cents/lb and the silica is $1.14/lb. Perhaps it would be different south of the border as the neph sy comes from Canada, and the silica from the US.
I believe the Minex 7 (neph sy) is about 4 microns as is the Minusil 10 (silica) - or so my sales person says. Why they aren't called Minex 4 and Minusil 4 escapes me - just to keep us all confused perhaps. This is pretty fine and as far as I am concerned , the finer the better. My rationalizing has it that the finer the silica, the tighter it packs when rubbed in, the less likely that water vapour will make its way through the canvas from the inside, and hopefully then no paint blisters. i had a short stint of paint blisters when I used some silica that was called 200 mesh (more confusing labelling) which I believe was coarser than 40 microns. My supplier had gotten progressively coarser grit silica and I didn't know that it perhaps could make a difference. It all looks like fine white powder but to a water vapour molecule it is probably like the difference between crushed stone and clay.
And I've also put cornstarch in filler.. Now that is really fine, and rubs out well. Not sure if it just gives the mould something really yummy to grow on though.
Why not try some cement ....Its fine, will dry concrete hard and we al know that it can be smoothed out and rubbed in!....:rolleyes:
i guess that if you wear a face mask and are careful......... anyway i don't worrry about it i just get the wife to do that part.

Wow, what a response to a complicated subject, and I couldn't get a single one on my query about whether or not to prime before paint. Too elementary, perhaps? Anyway, six coats on the old '24 and she's lookin' pretty good.:eek:
Ray in raaiinyy P. A.
Funny You Should Say That!

Blue Viking said:
Why not try some cement ....Its fine, will dry concrete hard and we al know that it can be smoothed out and rubbed in!....:rolleyes:

From my study of the stuff (i.e. reading, not using!), it seems silica is probably used because of its crystalline structure. If you add water to it and stick it in a kiln, it undergoes a change because of a fast with flame combustion process.

If you add a polymerizing agent to silica, the agent (oil) polymerizes by auto-oxidation which is a slow, flameless combustion.

So filling a canoe is not much different from either pottery or cementing.

I wrote up a lot of stuff on this but never felt confident enough to broadcast it!

I actually started looking into using an oil/cement mixture (again, theoretically) but ran out of steam on that! Too many reactions going on to make a guess at there!

Bottom line is that I think the silica because it is crystalline can line up snugly and bonds side-by-each (as we say in de Nort' Con-tree) in the polymer and probably adds a lot of structure to the material.
ACTUALLY!.....I do know a professional restorer who stated to me that IF I was in such a hurry to float my canoe that I could in fact use a porch and deck enamel and mix either cement or talcum powder to it until it reached a peanut butter consistency and it would dry in about 3 days and could be painted...It would float and be waterproof but the longevity was questionable becasue there was no history on its I opted to wait the 6-7 weeks and used the old tradional method. Now I am glad I was patient and have a WC Sebago boat and a 42 year old OTCA...both are now part of my fleet that is growing monthl....I now have 4 done and 3 to go...18' strip laker and my old favorite little 74 Stowe.(love this thing for just paddling and fishing when I need time alone) Out fo business until spring when I will finish my Chestnut and my White Boy SCout ( and these are old.)
BUT as far as CEMENT goes, I will do the traditional and wait the time it takes to cure. Who knows!!!!!.....I might have a couple more by then!:eek:
The traditional filler for the northern Manitoba Native communities is just linseed oil. Put that on the canvas, fill 'er up, then paint. This is an approach that probably developed for reasons of material availability. Seems to work.
:eek: Wanna be honest here....When I stripped the canvas off my chestnut, I was convinced that it was still yellowy and kinda wet under the paint...I didnt want to mention it because I thought I was losing it:) BUT...I am now convinced that that is what they did for this one...Just oiled it and painted it!..It was in really bad shape due to the paint curling and cracking That is why I love this forum...Even if your too embarrassed to ask a question, the answer will come when you least expect it
filler and oil

I know of one older builder, who doesn't oil the hulls of his canoes, but canvasses and then oils the canvas and the hull underneath all in one go. I have never been brave enough to try it, nor seen one of his canoes on recanvassing to know the longevity of both skin and hull.

And about chestnuts with the paint all peeling off in big chunks, I have thought that that happens because they did two applications of filler. The initial one that soaked the cloth with the oil and filled the weave, and then a second one that built up over the weave and left a smoother surface to paint on. It seems this second coat is the one that gets chalky and the paint loses all adhesion. That is why I only do the one application, and start painting over the very slightl weaviness - assuming that the paint will have better adhesion. Mind you if my canvas were to last 30 or 40 years as did the chestnuts, then perhaps I wouldn't be worrying that the paint was flaking off!!!
;) Thanks Pam!............I'm outta business until spring but I think I am gonna use a #12 on the Chestnut and try the silica and lead system...It worked good for me and now I am hooked on it!....The way you described how Chestnut must have done it describes what I encountered. As far as Porch and Deck paint and cement...NAAAAH!:D