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Silicone and Mineral Spirts Problem
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Richard Nisley
(richard295) - M

Locale: San Francisco Bay Area
Silicone and Mineral Spirts Problem on 10/10/2010 13:11:55 MDT Print View

I wanted to reduce rain splatter from big storms when using my silnylon Duo-mid. I mixed 9 oz. of Klean-Strip Odorless Mineral Spirits and 3 oz. of GE Silicone II. I don’t know the manufacturing date on the Silicone II but it appeared to be OK when I squeezed it out of the tube. I stirred it to make a uniform solution and then used a paint brush to apply it to the inside surface of my Duo-mid.

Three days later there is still an oily sheen on the surface and it wets my finger when I touch it. I took a cotton towel and wiped the surface down on one panel. That panel no longer leaves an oily sheen but it still has a "wet look".

What happened and what do I do next?

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Silicone and Mineral Spirts Problem on 10/10/2010 15:18:53 MDT Print View

Hi Richard

First of all, the water you have been getting on the inside of your Duo-mid is almost certainly condensation, not leakage. While current silnylon is not great, the pressure rating is enough to handle rain and storms. So putting on a second coating won't solve your problem of spray.

GE Silicone should be OK, but I have NO idea what is in 'Klean-Strip Odorless Mineral Spirits'. Current USA regulations permit the manufacturer to include anything, and to change the contents as well. I suspect, although I do NOT know, that the oily sheen may be just that: some sort of oil included to help strip off paint. It is probably not very compatible with silicone chemistry either.

Wiping the oil off is rarely easy, so the sheen is probably residual oil still there.

What to do next? Good question. You could try lots of sheets of newspaper to soak the oil off.


Acronym Esq
( - F

Locale: TX
Re: Silicone and Mineral Spirts Problem on 10/10/2010 15:19:25 MDT Print View

I did the same thing to my silnylon tarp except I used Coleman white gas instead of mineral spirits. My treatment dried, but it did leave a glossy finish where I applied the silicone.

I think you should pitch your Duo-mid in the back yard, wipe the oily wetness off, spread some newspaper under the tarp, and turn the sprinkler on for an hour. If the tarp is leaking the newspaper will get wet.

I suspect your application worked.

acronym 10/10/2010 4:17 PM

Danny Wang
(gnawd87) - F
klean strip on 10/10/2010 21:53:03 MDT Print View

Its probably from the klean strip mineral spirits. I bought the same klean strip odorless minerals spirits last time i tried to seam seal my tent. i mixed it GE II silicon as well and the mixture didnn't look right at all. It was a milky like texture that i ended up not using. There probably something in it that's giving your duomid the oily/shiny look. I say wipe off what residue you can and if it doesnt affect the waterproofness of the shelter then just live with the shiny-ness and next time use a different mineral spirit.

Edited by gnawd87 on 10/10/2010 21:54:05 MDT.

Scott Toraason
Klean Strip on 10/11/2010 10:49:41 MDT Print View

It has to be the brand of mineral spirits. Having sealed two Stephensons using GE Silicone 2 with a good mineral spirits my mixture was dry within hours. I used a 50/50 mixture but more mineral spirits just makes for a thinner solution.

Mary D
(hikinggranny) - MLife
Kleen Strip? on 10/11/2010 13:12:30 MDT Print View

I just checked the can of mineral spirits that has been in my garage since I bought my first Tarptent in late 2005. The brand is Kleen Strip. However, I've had no problem with oily residue. I suspect the forumula of the brand may have changed?

Considering that I still have at least 3/4 can of the stuff left that I'll probably never use, and I have had to throw away at least two tubes of the GE Silicone caulk that hardened on the shelf in the intervening years, I think I'd have been better off just to buy and use SilNet for seam sealing the several tents I've purchased in the last 5 years.

Edited by hikinggranny on 10/11/2010 13:13:40 MDT.

Henry Shires
(07100) - F - M
Re: Klean Strip on 10/11/2010 13:46:13 MDT Print View

I concur that something went wrong with the chemistry and that it's likely the mineral spirits. FWIW, we buy gallons of "Sunnyside paint thinner (low odor mineral spirits" from the local hardware store and have never had a problem with the chemistry but I have heard of and seen several cases of seam-sealing that went very wrong.


Marc Penansky
(MarcPen) - F

Locale: Western NC
Silicone and Mineral Spirts Problem on 10/11/2010 13:51:36 MDT Print View

I have had a similar problem in the past and I seam seal a bunch of tents on an ongoing basis. I had a partially used tube of GE Silicone II and mixed it with Klean Strip Odorless Mineral Spirits and tried it out on some spare pieces of sil-nylon as well as some caulk right out of the tube. The mixture never seamed to dry and had an oily sheen on the sil. The raw caulk never cured normally, was still wet after a few days and when it did dry, it did not adhere to the sil very well. I went out and got a new tube of Silicone II and used the same bottle of Klean Strip and did the same tests with much better results. The mix dried overnight and the bead of caulk cured and dried normally. This obviously points to the Silicone II as being the culprit but not sure if it had just been sitting around too long, was contaminated in some way, or what the problem was with it. I normally use a closer to 1:1 mix because I can control it better, but I don't think this affected the results.
I hate to disagree with everyone above (OK, maybe I don't) but I think it was the caulk. Try a similar test to prove it.
Now, what to do with the Duo-Mid? Not sure of the best solution here. If you are happy with the results of toweling off, go for it. Try some tests on a spare piece of sil and see if recoating it with a "good" mix will cover over the problem (before or after toweling off the residue).
I hope this post helps as I feel indebted to you for many of your insightful and information rich posts in the past.
Marc Penansky
LightHeart Gear

Rick Dreher
(halfturbo) - MLife

Locale: Northernish California
Re: klean strip on 10/11/2010 13:57:08 MDT Print View

From the Klean Strip msds:

Hazardous Components (Chemical Name)
Hydrotreated light distillate (petroleum)
CAS #64742-47-8
100.0 % Concentration

Yeah, this isn't very helpful as a description. I suppose as an experiment, you could let some of the solvent evaporate in a container and see whether it leaves anything behind. It seems likely there's some fraction of the ingredients is not volatile at stp, and that's the residue source.



Andy F
(AndyF) - F

Locale: Ohio
Re: Silicone and Mineral Spirts Problem on 10/11/2010 14:41:21 MDT Print View

I've done extra silnylon coatings using the same brand of everything you used. I used the newest GE Silicone II caulk which is for windows and doors (window and door: rather than kitchens and bathrooms.

Maybe the kitchen and bathroom stuff has a mildew-preventing additive which is leaving the oily residue?

My coating dried quickly with average humidity and temps in the 80's F.

I'd towel it down, pitch it inside out, and then spray it with the garden hose.

Tohru Ohnuki
(erdferkel) - F

Locale: S. California
permatex on 10/11/2010 16:37:47 MDT Print View

I've had good results from permatex flowable windshield and glass sealer from the auto store. It's already thinned and does a good job soaking into seams...

Danny Wang
(gnawd87) - F
Re: permatex on 10/11/2010 17:59:17 MDT Print View

That stuff is great for seam sealing but i think the OP was trying to paint the inside panel of his shelter to reduce misting not sealing the seams. permatex would be much too thick to paint on and you would need many tubes.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Re: permatex on 10/12/2010 03:48:58 MDT Print View

> permatex would be much too thick to paint on and you would need many tubes.

I disagree. I resealed an OLD silnylon floor in a hotel room in Italy using very similar stuff, with no solvent. It worked fine. I just had to spread it very thin with my fingers! :-) Yeah, took a bit of care and time, but it worked. I should add that some years later I am still using the same tent.


Phil Barton
(flyfast) - MLife

Locale: Oklahoma
Re: Silicone and Mineral Spirits Problem on 10/12/2010 05:03:18 MDT Print View

Timely discussion as I need to apply seam sealer to 2 new pyramid tarps.

One of the new shelters is a MLD Duomid that included a 1.5 oz tube of Silnet Silicone Seam Sealer.

What is the experience in using the Silnet product? Do I need to thin it with a solvent? What have you used?

In the past I've used GE Silicone Caulk II with mineral spirits. Seemed to work ok. Wondering if there is a better experience with Silnet.


james w glenn
(bark-eater) - F
silicone caulk trivia: House hold caulk tends to be acidic. on 10/12/2010 06:48:24 MDT Print View

Im not sure if this is relative to this discussion, but house hold silicon caulking is supposable acidic, while marine silicones are a more neutral ph. This makes a difference preventing crevice corrosion of stainless fittings in a marine environment I don't know if the acid would be a plus or minus when sealing a fabric.

John Kays
(johnk) - M

Locale: SoCal
right mixture on 10/12/2010 20:43:11 MDT Print View

I had the same problem sealing a tent with silicone and mineral spirits the first time. It was super oily and never seemed to dry. Later with other sealing projects on silnylon the mixture improved with just a small amount of spirits to silicone. The mineral spirits can was purchased at Home Depot. Brand unknown.

Craig W.
(xnomanx) - F - M
Silicone Trouble on 10/12/2010 22:17:45 MDT Print View

I had the exact same problem sealing a Tarptent. I used clear GE Silicone II and mineral spirits- the Home Depot brand people mention.

Exactly the same- 2 days later it was still wet/oily.

I called Henry Shires for advice. He suggested it could be a bad batch of silicone.

I wiped everything off as best I could (read: mess) and did it again. Same mineral spirits, new but same type of silicone(GE silicone II again). It worked fine.

I believe it's your silicone, not the spirits.
The original silicone I used never did dry- even in the tube. Something was wrong with the batch.

I've used the same combo since then and it's always been fine. I believe it was a one time bad batch.

Greg Mihalik
(greg23) - M

Locale: Colorado
Re: Silicone Trouble on 10/12/2010 22:22:43 MDT Print View

Interesting observation on the silicone.

I was going to caulk a tub. The tube was unopened, but a year or two old. I laid down a test bead on some wood. It never set up.

Bought a new tube. It set up fine.

Thought "it could only happen to me".

Edited by greg23 on 10/12/2010 22:23:22 MDT.

Rick Dreher
(halfturbo) - MLife

Locale: Northernish California
Re: silicone caulk trivia: House hold caulk tends to be acidic. on 10/12/2010 22:39:57 MDT Print View

There are different formulations, and the earlier stuff indeed contains acetic acid, you can tell from one sniff.

The GE silicone II does not and seems to be what most folks use.

I bagged mixing the stuff in solvent because it seems to form a suspension and not actually dissolve, so requires nearly continuous mixing. I bought the best caulking gun I could find (stepless action) and apply the stuff full strength, straight from the tube. It's not the prettiest and may result in an extra few grams of sealant when the job's done, but it's faster and gives a complete seal. One tube will do two or three of the most complicated tents, while SilNet might need three tubes/shelter. An electric gun might be better but I've never used one.

(Of course, this is for sealing seams and not re-coating the fabric.)



Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Re: silicone caulk trivia: House hold caulk tends to be acidic. on 10/13/2010 03:04:08 MDT Print View

Hi Rick

> I bought the best caulking gun I could find
I transferred the Permatex stuff and some other stuff into a large hypodermic syringe (without the needle) and used that. It worked REALLY well. I normally run a thin bead along the seam on the pitched tent, then smear it down with my finger to make sure it goes INTO the seam. I don't need a lot.

You should be able to get an empty 20 cc (or 50 cc) hypodermic from a doctor or a pharmacist (or a vet) if you explain what you want it for. The vet is likely to have the larger size ... for horses.

Now for the bonus point. The plastic hypodermic syringes are made from polyethylene, and silicone does NOT stick to PE. Does not stick to the black rubber seal either. So when I am finished, I pull the plunger out and let it all set. A day later I just peel the cured silicone off the hypodermic bits and put it away for next time.