Mildewcide

[ed4353]

I know this topic has been discussed multiple times here, and I apologize for bringing it up again. However, regulations change so fast, that a mildewcide that was available 2 years ago may be just a distant memory now.
I'm interested to hear what others are using, and their experiences with mildewcides being used for the canvas, and as an additive to the linseed oil/mineral spirits for coating the hull, etc. I have found copper napthenate, which is the preferred chemical of choice, but it's green and I have read that it can bleed through. Next is zinc napthenate, which is clear. I found one product with that (made by Green's, as well as the copper napthenate), but it also contains wax. Not sure if that will interfere with the filler. There are several paint additives that will work with water or oil based products, and am leaning toward one of them (Add-2, made by Zinnser). It's locally available. They contain a chemical with a name that was never meant to be pronounced by any living human being.
If anyone has any experiences with any of these, or other products available today (in the US), I would be grateful to hear about it.
Again, I apologize for re-hashing an old topic, but I feel it needs to be updated with current information.
Thank you.

Ed

 

[Todd Bradshaw]

Probably controversial and certainly not traditional, but since the tests done by the Forest Products Lab showed linseed oil to be a very good food for rot, it seems odd to be trying to kill stuff like that on one side of the wood/canvas junction and feeding it on the other side. My first step would be switching to an oil product like Deks Olje #1, which is a lot less tasty to mold, mildew and other nasty stuff.

 

[mccloud]

[QUOTE= tests done by the Forest Products Lab showed linseed oil to be a very good food for rot

I've seen this comment several times by several authors, and have tried to find this information via a Google search, but have not been able to locate the study. I want to read it myself. Can someone point me to the primary source? Thanks. Tom McCloud

 

[Howie]

I've been told that you can use stuff called Krud Kutter MC2 mildewcide. It contains something called benzimidazole according to the packet. I was advised to add one or two of the 0.35oz packets to one gallon of filler, and that with it you could use untreated canvas. I haven't tried it yet, but figured I'd start using it with the next canoe.

 

[ed4353]

Todd...
That's an interesting idea that I never considered. I'm going to look into it. My first 2 questions would be:
The fillers all have linseed oil in them. Can this oil be used in it's place in the filler?
The cotton duck is itself a great food for mildew, which brings me back to the original question of which mildewcide to treat the canvas with (if buying untreated canvas)? Or, is mildew in the canvas itself is not a problem, if the linseed oil is removed from everywhere else (sealer and filler).

Howie...
I believe Krud Kutter uses the same active ingredient as the ADD-2. The parent company owning both products in Rust-Oleum. The store I went to sells the ADD-2.
I may just suck it up and use it. It's only mildew on a canoe that I invested several hundred hours and a pile of money in.

Thank you all for your replies.

 

[Todd Bradshaw]

- Deks #1 is as thin as water, so I doubt it would be good for making filler. As a wood sealer though, its ease of application (slop on as many coats, wet on wet, as the wood will absorb, wipe off the excess and it will probably be dry to the touch the next day) makes it hard to beat from the options I've tried.

- Mildew on cotton fabric is always a concern, and worth doing whatever you can to the fabric to help prevent it. Unlike synthetic fabrics where it's just ugly, mildew actually eats cotton fiber over time and weakens it. It needs air, moisture and decently warm temperatures, along with a food source to survive (the cotton itself, plus any dirt or other stuff that finds its way in there). We can't get rid of the first three on a canoe, so poisoning the food source as much as we can would seem to be the best bet to help prevent it.

- As mentioned, finding things in the Forest Products Lab's website is quite a challenge. I looked, but couldn't find the paper that I read 10-15 years ago about linseed oil being rot food for wood. Searching under "linseed oil" for anything pulled up very few hits. I did find one paper that had at least one paragraph that was along the lines of what I said above about putting linseed on a surface next to the canvas. I had to do a screen capture and then my computer froze, but I got this part OK. The paper is here:

http://www.mchd.com/pdf/woodpr.pdf

 

[mccloud]

I read the reference that Todd posted above, and it is worthwhile. It is significant that it distinguishes between mildews, which live on the surface of wood but do not degrade it, and wood rotting fungi. The purpose of this Forest Products study is to determine water repellency conferred to wood by various additives, and also demonstrates the benefits of adding a fungicide to the formulation. In their listing of these preservatives on page 7, at the top of this list is 3-iodo-2-propynyl butylcarbamate. This is the active ingredient found in M-1 mildew treatment which you can buy at Home Depot, and add to paint. I have used this product, applying it to red cedar, canvas and filler at various times, but it will be years before any opinion of its effectiveness is known.

Linseed oil has been used in many water-repellency formulations, but it can be eaten by fungi. Much less digestible to fungi are boiled, partly polymerized, or alkyd oils. Dryers, i.e. Japan Dry, are metal catalysts that accelerate the oxidation & polymerization of linseed oil. Linseed oil, tung, and others are sometimes used in fungal fermentations because they can be utilized as food by the fungi, but there are a couple significant differences between this situation, and putting linseed onto cedar - first is that no fungal growth occurs in the absence of water, of which there is plenty in a fermentation, and second, that liquid raw linseed oil is not the same thing as boiled, polymerized linseed oil. How many of you eat raw, hard, uncooked beans? That's the equivalent of polymerized linseed oil. Cooking the beans makes them digestible to people, while polymerization of linseed makes it rather undigestable to fungi.
Continuing to search for information about linseed oil, I found another Forest Service publication that applies: http://www.fpl.fs.fed.us/documnts/finlines/finishline_mknaebe_2013_002.pdf
Is this the one you were trying to locate, Todd?
Canvas is much more digestible to fungi than wood, so that's where antifungal substances need to be applied. I've used the fungicide-treated canvas that Rollin sells, and I asked him one time if it was washed off by water. He said no. I asked what the compound was, and his answer was that it was some long, unpronounceable chemical.
So I am still searching for information about linseed oil, and the fungi that love to eat it.
Tom McCloud

 

[Todd Bradshaw]

I read that one the other day during my search, but it isn't the old one that dealt with linseed oil being good food for wood rot. As I remember (it's been quite a while) the original was not about making a home-brewed wood finish. It was more oriented toward just testing the effectiveness of the oil. I'm sure I'll probably find it again within the next ten or twenty years. In the mean time, I'm learning a lot about things I don't care about, and scientific stuff that is way over my head.

 

[Shaun]

Wood, cotton (canvas), and oil based paint will all rot (break down by microbial action) in the presence of oxygen and moisture. This can be slowed but not prevented by some compounds. There are natural compounds in some types of wood that slow the process. Any wood that makes a good fence post contains stuff that slows this decay. The very best way to prevent decay is to keep the item dry most of the time or at least let it dry out between uses. The most common areas of canvas rot seems to be at the gunwales and especially at the tip ends where they rest against the ground when left outside upside down. If we all had indoor or at least roofed areas to store our canoes and put them there between paddles, there would be no problem.

I read the label on a can of Petit Easypoxy paint recently - a popular brand for restoration. It states that it is not meant to be left in contact with water for more than two days. The paints we generally use are not "bottom" paints which contain high copper or other heavy metal content.

Birch bark canoes were sometimes winter stored by sinking and weighting down with rocks. This removed the other rot component oxygen.

Anything that will prevent (actually slow down) the decay process is by definition poison to living things like mold and humans. Lets be careful when using this stuff, ie read and follow precautions. This includes taking care not to breath the dust of toxic wood when sawing and sanding. As a long time carpenter I have found the following woods to be toxic, in descending order of my reaction; yew, osage, walnut, mahogany, western red cedar, white cedar. Wood labeled CCA (we used to call it Wolmanized) is also toxic from the heavy metal added to slow decay. CCA wood is so toxic that the warning label says not to burn it because of the fumes released.

So, lets make rational decisions about this stuff, keep our canoes hanging in nice dry places between use, and for heavens sake don't set them on fire!