Grinding sanding dust further to make wood flower?

[ernie]

I have been using sanding dust as a cheap thickener for epoxy, but it is still rough.
Any ideas how to make even finer powder, other than to start sanding everything with 250 grit paper?
I don’t quite dare do this in any crucial joints, dose anyone have experience or strength test data for this type of filler?

[Toot]

You could just buy microballoons/bubbles or silica or whatever.

I use a lot of microballoons. You can get a pound of them for less than ten bucks and a pound of these things is a LOT. I'd guess it's almost a gallon's worth.

At such a cheap price, why not use them?

[frosh]

Ernie, thickeners for epoxy to make glue or fillets or fairing compound is a lot more scientific than adding wood dust. Also they are the cheapest component in boat building. If you can't afford them then how can you afford the structural materials? I use three types of filler. (1) Microballons
(2) Microfibres (3) Thixotropic Silica. Sometimes they are combined and sometimes not, depending on the exact purpose of use.

[Frosty]

I notice that talcum powder was not mentioned. I know nothing about this kind of stuff but do use talcum for thickening. Is this not the right thing to do then?

[Toot]

I don't know how well talcum powder would work. On the one hand, it's a mineral, right? So it shouldn't absorb epoxy and cause a risk of a dry bond. On the other hand, I don't know enough about its properties to say how well it might work.

Can you really get talc for less money than microballoons or milled glass?

[Frosty]

Talc is all I know of, its what everyone round here uses. I buy it at the fibre- glass shop that sells all the other stuff. My wife tells me it is 1kg per 15baht,-- there is about 40 baht to a US dollar. 2kg is about a gallon. Big gallon 4.4 liters.

Its not the smelly stuff that you put under your arms,-- but I guess you could!!

As far as it being a mineral --not a clue!! Milled glass???? dito.

I can get micro balloon stuff,--but bit expensive? I once filled an old dinghy keel with sago milk pudding powder,, it worked well !! Theres also vanilla flavour custard mix-- , or tapioca flour. I dont suppose the flavour really matters.
I am not joking,-- well, just a bit on the flavours!!!

[gonzo]

Talcum absorbs a lot of humidity which can be a problem. It was used in the early days of fiberglass and found to be of poor performance. You will never see it in quality construction. Fillers have characteristic that are are specific to each use. It is foolish to risk a major failure to save a little money.

[Frosty]

Ok-- but if it were to be used as a skim to fare off a particular shape and then glassed in, it would be ok would'nt it? Such as skimming foam to make a nice smooth surface on which to glass over?

[Toot]

Honestly, I'm trying to approach this with an open mind. I don't want to say don't use it if my only justification for saying so is that "It sounds wrong".

However, don't think I'd use it to skim foam. This is what I was talking about a few weeks ago when I was talking about using slurries. In that application, you want a very strong structural bond between the foam and the glass. This is definitely a structural application. Where I might use it, however, is for non-structural fillets, such as places where you just want a smooth rounded contour and strength doesn't matter... but again, if the fillet is going to flex or carry any weight, then I'd opt for something else.

[Joe6]

In my opinion ideas like this end up in wasted time that would be better spent working. Just buy the stuff and save the hassle.

That said, I'm not criticising you, I've tried everything mentioned on this page and more!

Can't blame a guy for trying to save money, but in this realm I think its better to just spend the $10 and get on with the work.

I once tried 320g linear polyurathane sanding dust harvested from my dust collection system mixed with epoxy, it worked, tough to sand.

Back in the seventies a friend of mine used lime (the stuff used to put lines on football fields) mixed with polyester resin (by the drum)to fair a 90' alden schooner.
It also worked, absolute murder to sand.

Joe

[ernie]

Maybe it’s me, but it just feels wrong to spend money for a filling powder when you can’t feel the weight of it.

But as for as structural integrity goes, the sanding dust is the same stuff as the rest of the boat, so with regards to epoxy adhesion, water absorption and other characteristics, why isn’t this as good as anything else?

I am aware of the special properties of products like colloidal silica and micro balloons, but extra flexibility and super adhesion (more than epoxy alone) are not necessary for every job are they? Especially the large amount of filleting in a stitch and glue project. Obviously scarfing a joint requires something else, as dose the bedding of a mast step or motor mount.


It isn’t a matter of what can be afforded, I just bothers me to pay for a product called wood flower, then go to the shop and dump what seems to be the same stuff from the collection bag of my sander in to a landfill.

But it would be better if I could make the stuff from my sander more consistent.

[bilgeboy]

Ernie, I appreciate your sentiments.

I agree with your views 100%. You should save the dust you collect with 220 grit and up. Why not? Just because you live in the US doesn't mean you should throw out the perfectly good, and replace with the latest and greatest. Hell, you can sell it to boat builders!

Something more interesting to me is that I bought a gallon a few months ago, don't even remember what I paid. I didn't care at the time, I was in a hurry, and bought a big ol' jug of wood flour at Jamestown Distributors.

I never do that. I never walk into the Home Depot and buy "wood". "Could I have some wood, please?" I generally have a clue about the relative weight, rot resistance, grain tightness, etc, etc, etc. But I actually went and happily paid for saw dust of a completely unknown species.

You are creating a composite compound when you mix the flour with epoxy, and there must be good flours for certain applications. To say there is no real difference for this application would be like saying glass and carbon are the same when used with epoxy.

I say go for it, ernie, and let us know which species you like.

Mike

[Frosty]

Thats a good point about the dust being from the boat in the first place. What could be a better thickener than epoxy powder in epoxy to make thickened epoxy?

I am so pleased that i am not the only person to have tries 'custard mix' I am not sure what exactly is 'custard mix' but can it be any worse than foam itself. After all its just meant to fill it out a bit to thicken it?

I used rice once!!! But if its enclosed in epoxy how can any thickening product absorb moisture.

Maybe 'Bisto' thats made to thicken.

Ok joking again, but putting the expense aside I feel sure there must be something in the supermarket that could be a substitute. This modern world of re-packaging makes one very suspicious.

[marshmat]

Not sure how sawdust works in epoxy since I usually work with carbon and such these days.
In my experience with polyester, sawdust proved to be a good thickener but didn't actually extend the volume at all. It made a cup of thin resin into 1.05 cups of gooey resin. The microballoons increase the volume a lot more for the weight.

[fiberglass jack]

one time i was working on a field job a days drive from the shop, we forgot to bring cabosil with us to make paste, couldnt get any where we were up in a mining town in northern canada, so off to the local supermarket and bought flour worked good that was 12 years ago dont know how it would be with epoxy , if your going to make a paste thats going to be sanded and faired go with good stuff the money you save will only be spent on sand paper

[frosh]

I made a curry once that was very runny. My wife suggested that I add some fine corn flour. It worked a treat, and even tasted good. No science was needed for this solution.
Boatbuilding is a different kettle of fish. And the proper stuff is as cheap as chips; by the way does anyone enjoy chips with their fish? :rolleyes:

[fiberglass jack]

only if you got some malt vinager, your right materals is cheap but some boat owners are cheaper really cheap

[Frosty]

Cheap or not so cheap, that is the question. I must be nice to be able to get iether. I think the emphasis is on the fact that it is possible to get away with a substitute and how good that substitute is. I for instance here on a small island west of Malaysia have a choice of 1 shop-- when they open!!, they have micro ballons (what ever they really are) and I think they were asking 26 dollars for a small bag about the size of a childs pillow or lap top.

So having ALL the time in the world I see nothing wrong with a bit of inginuitive thinking in the super market while the wife looks at hair dye.
Personally and I am by no means any kind of expert in this field but have had an unquestionable success with talc, It sands great!!

I cant get over this thing about absorbing moisture, if a material absorbs moisture in its container open or shut on the work bench,-- well ok but how can it asorb anything when it is totally emersed and surrounded by epoxy or resin? If its going absorb any thing then absorbing epoxy would be good no?
OR is it that talc will absob moisture to the point that it is unsuitable as a filler? in that case then we should say that talc has a short shelf life, but is in fact a good filler when fresh and dry??

Im fighting for Talc here simply because its all I can get( cheap) and its all I've been told I need ( localy) for my littel project' advise needed for foam job" Thread

[Joe6]

I've heard that talc works well, but I've never used it personally. But if it were all I could get, it's what I would use!

Joe

[gonzo]

Some materials, including fumed silica absorb water before being mixed. Containers must be kept well closed. Fumed silica, like lime has been fired in a kiln which takes all the water out; even the chemically bonded portion. It is always possible to lower quality and make something cheaper. However, if you use your own formula instead of what the resin manufacturer recomends, there is no warranty. That is, unless you provide one. Sanding dust is contaminated with all kinds of foreign materials. The worst is the surface wax. When resins cure, polyesters, vinylesters and epoxies, there is a layer of wax that migrates to the surface. That is why it needs to be sanded and dewaxed for proper adhesion of future laminates. You are adding all the wax residue to the mix with unknown results. In other words, you are incapable of providing any engineering calculations because the properties of the mix are unkown.

[SamSam]

I bought a big bag of Cabosil at a fiberglass supplies wholesaler a long time ago. The salesman said they sold a lot of it to McDonalds to put in their milkshakes to thicken them up. Maybe in an emergency, you can order a milk shake without the 'food' stuff.;) Sam
http://www.cabot-corp.com/cws/businesses.nsf/CWSID/cwsBUS01122001013247PM7861?OpenDocument

[ChrisF]

Well there you go. Obviously McDonalds could substitute and use flour in their food, but do they? No, they use the real thing, Cabosil, and if that isn't proof that it's better I don't know what is.

[Frosty]

What is Cabosil any way? It must be edable if Mc Donalds use it,-- well maybe not!!!!. If thats true then it must be cheaper . It seems like there is so much stuff to thicken stuff with.
After all said and done is it not just a method of increasing its viscosity for ease of handling for a particular application?

[frosh]

McDonalds, the most successful company in history, (slightly more successful than Coca Cola) uses Cabosil (thixotropic silica). They could be using the kids they employ for about $4 an hour to sand down chip board to create really cheap wood dust to thicken milk shakes, but they don't. This would save around $10,000,000 a year worldwide based on selling a billion milk shakes per annum, but they see it as false economy leading to a loss of market share.
Now I ask all you cheap skates, is your boat project more or less structurally sound than a McDonalds thick shake? And, would you like it to be?

[ChrisF]

Frosh, I understand it's actually a problem with the chip board supply that prevents McDonald's using it to thicken shakes. They're stretching the supply chain as it is, just to get enough to make burgers. Unfortunately the hole saw dust from the burger making process is too coarse for thickening shakes. Which brings us back to the original post, I guess.

[mobjack68]

Hey ernie, think thru your application, the harder the filler (lime, talc) the less flexible the fillet, matters not the cost. If you are using a material that leaves a less than desirable finish, cover the wet material with a strip of Saran Wrap, smooth it out w/ your finger wait for it to set, peel away the plastic, scuff sand and keep on keepin on. Test your plastic wrap for reactivity before covering a large area, stay away from waxed paper unless you specifically need the wax...
mobjack68

[Richard Hillsid]

I don’t feel up to typing right now but there is more to fillers than volume, you get elasticity, hardness, compression, sheer strength and numerous other qualities with them, microbaloons are ok in some application, but definitely not when looking for strength, wood dust, not in a production boat.

Here is a oldie system there are many other products on the market but most have used these at one time or another.




Filler Selection Guide
http://www.westsystem.com/webpages/productinfo/guide/Filler_select.htm

-----------------------------------------------------
Adhesive Fillers vs. Fairing Fillers

http://www.westsystem.com/webpages/productinfo/guide/index.htm

Fillers are used to thicken the basic resin/hardener mixture for specific applications. Each filler possesses a unique set of physical characteristics, but they can be generally categorized as either Adhesive (high-density) or Fairing (low-density).
Adhesive filler mixtures cure to a strong, hard-to-sand plastic useful in structural applications like bonding, filleting and hardware bonding.

Fairing filler mixtures cure to light, easily sandable material that is generally used for cosmetic or surface applications like shaping, filling or fairing.

ADHESIVE FILLERS

403 Microfibers
403 Microfibers, a fine fiber blend, is used as a thickening additive with resin/hardener to create a multi-purpose adhesive, especially for bonding wood. Epoxy thickened with microfibers has good gap-filling qualities while retaining excellent wetting/penetrating capability. Color: off-white.

404 High-Density Filler
404 High-Density filler is a thickening additive developed for maximum physical properties in hardware bonding where high-cyclic loads are anticipated. It can also be used for filleting and gap filling where maximum strength is necessary. Color: off-white.

405 Filleting Blend
This strong, wood-toned filler is good for use in glue joints and fillets on naturally finished wood. It mixes easily with epoxy and lets you create fillets that are smooth and require little sanding. Its color is a consistent brown, so 405 can be used to modify the shade of other WEST SYSTEM fillers.

406 Colloidal Silica
406 Colloidal Silica is a thickening additive used to control the viscosity of the epoxy and prevent epoxy runoff in vertical and overhead joints. 406 is a very strong filler that creates a smooth mixture, ideal for general bonding and filleting. It is also our most versatile filler. Often used in combination with other fillers, it can be used to improve the improve strength, abrasion resistance, and consistency of fairing compounds, resulting in a tougher, smoother surface. Color: off-white.

FAIRING FILLERS

407 Low-Density Filler
407 Low-Density filler is a blended microballoon-based filler used to make fairing putties that are easy to sand or carve. Reasonably strong on a strength-to-weight basis. Cures to a dark red/brown color.

410 MicrolightTM
410 MicrolightTM is the ideal low-density filler for creating a light, easily-worked fairing compound especially suited for fairing large areas. Microlight mixes with greater ease than 407 Low-Density filler or microballoons and is approximately 30% easier to sand. It feathers to a fine edge and is also more economical for large fairing jobs. Not recommended under dark paint or other surfaces subject to high temperatures. Cures to a tan color.

Filler Selection Guide
Filler Buying Guide

[chandler]

I save all the sandings from laminations, all the sandingings from fairing...get a pretty good combination of fine sawdust mixed with sanded epoxy powder.
Pretty much any composite construction is going to be coated with epoxy and glass so I think the water absortion thing is a mute point.
Just keep recycling your dust.