The Caulk Option

[Roger C H]

I know that Silicon is bad.

I know that Butyl is good.

But what about Latex, Acrylic, Polyurethane, etc?

Anyone have any experience with other types?

[Raya]

Hi Roger,

A lot depends on what you are planning to use the caulk for. What application, and what materials are involved (plastic, metal, etc.).

In general, I'm not a fan of latex caulk for the typical uses on our campers. It's just not rugged enough. And you know what I think about silicone I tend to go with butyl or polyurethane. There is a caulking application chart I like; let me see if I can dig it up and post it here.

Raya

[Raya]

I haven't yet found the (simpler, more old fashioned graphically) chart I was thinking of, but here is one put out by 3M. If you want to use a caulk of another brand, you just have to "translate" to what basic type they are talking about and then figure out the equivalent.

For example, 3M 4200 and 5200 are polyurethanes. 3M 101 (discontinued, I believe) is a polysulfide. Sikaflex 291 is a polyurethane. Boatlife's Lifecalk is a polysulfide, and on and on.

Then within the types, there are usually sub-types with greater or lesser adhesion and/or stretch values. These are quantified in *another* chart that I will have to dig up, so that you can really compare and contrast and choose, if you want to get that specific. If not, you can go by the general characteristics. e.g. 3M 4200 is a polyurethane for use when you plan to remove the item; 3M 5200 is a "permanent" polyurethane (it isn't, really, but it's a *&%?# to remove, so I only use it on "semi permanent" projects).

I have to leave the house pretty soon, but I will come back and post more info later. [Note: Found and posted below; it's the black-and-white one.]

Let's see if these are at all readable:

[Raya]

[David Schroeder]

Latex is useful for short term fixes. Removes easily with no residue.

[Raya]

Aha! I found the chart I was looking for. Credit goes to the Jamestown Distributors catalog, although I don't see that they publish it anymore.

This chart gives you a measurement of the adhesive power, tells you what "family" of material the various brands are (i.e. polysulfide, polyurethane, etc.), and more.

Note that there are three parts; they "stack" one above the other.

[Raya]

Note that I do not endorse the use of silicone, even if it says "marine" on the label

For plastics that will be damaged by the "poly" family, I prefer butyl (of course check for compatibility on your specific project). If I remember correctly, Rule (brand) Elastomeric caulking is a butyl. It can often be found in marine catalogs.

There are other brands of caulking, of course; this is just a representation of some popular brands.


Raya

[Roger C H]

Wow! Thanks for all the information. I, unfortunately or not, had to use the stuff in my hardware store. It looks like it would be really good, but it is thick!

http://www.sashcocontractor.com/Home...ent/Lexel.aspx

Thanks again. Will let you know how the Lexel works out. There are nine pop rivets on my door shield and each has a hole which seems bigger than the standard household size pop rivet. No wonder I was getting water inside.

[RSchleder]

For items that need caulking on the roof ( or any other flat surfaces), you can't beat C-10. It's made to adhere to fiberglass, is self leveling and can be bought at most RV dealers/parts outlets.

[Raya]

RSchleder,

When you say "self leveling," does that mean that you are using it on *top* of the hardware or fasteners? I'm guessing so, because when it's under the flange, self-leveling wouldn't be a factor.

At any rate, I just want to be clear that when I'm speaking of caulking, I talking about using it *under* the flange or hardware piece, as you install it. Examples would be a window frame, a roof vent, or, say, an electrical cord inlet base.

I seal hardware and fixtures in the boating world, where they get a serious workout (saltwater, flexure of structure, immersion), and we don't tend to put any caulking or sealant on top of fasteners and/or hardware, but instead underneath, during installation or re-bedding.

I do notice that on boats and campers, leaking hardware/fasteners are often caulked on the top to try to solve a leak without re-bedding, but this seldom works and tends to be unsightly as well (blobs, gathers dirt, etc).

If you're recommending the C-10 as a bedding, then... never mind! I'm not familiar with it, but "self leveling" caught my eye, hence my elaboration.

Raya

[Ray N]

For a very small leak, you might want to try "flowable silicone," (oh no, not silicone). It is very thin and will seek out hairline cracks and fill them. I used it to fill between a tail light lens and the rubber gasket where there was a small leak. If you use too much on a vertical surface it will flow to the bottom and puddle, or even continue to flow on down the surface; so stand by with paper towels to wipe up any excess before it runs too far. It's sold in auto parts stores as "windshield and glass sealer." Again, it's silicone, so use judicially with fiberglass to avoid the well-discussed silicone problems.

[HerseyBA]

"Again, it's silicone, so use judicially with fiberglass to avoid the well-discussed silicone problems. "

OK, I'll take the beating. For those of us who have missed the discussion, how about a 25 words or less discussion as to the problems.
Thanks
BAH

[Raya]

Oh, don't MAKE me rant about silicone again

Let me dig up my rant from the other day in Jen's thread, and I'll add it here

I'll preface by saying that I don't know all "worlds" of caulk use. I'm quite familiar with boats and campers; and somewhat familiar with houses and cars. But not skyscrapers, etc. (I know "structural" silicone is used to put large glazing panels on skyscrapers, for example, but I can't speak to it.)

Okay, modified rant from the other day (recycling points! )

Butyl is *not* just "old-school" -- it works amazingly well. And if you did want to be more modern, there are things like polyurethane caulk and others. Never silicone! [on a fiberglass camper] I pray that anyone reading this (and you for future windows) gets the message. I rarely post with such firmness about techniques, but, in my opinion.... no silicone! Yes, this is probably as close as I get to a ranting, drooling lunatic; I have had to remove much DPO silicone in my life (mostly on boats).

Here are my reasons:

1) It does not do a great job of sealing; there will be something better for 99.99% of sealing operations (maybe 100% on a fiberglass boat or camper).

2) When you have to remove it...

3) Even when it *is* finally gone (or so you think), and you are lying, spent, on the garage floor with every last curse sucked out of you (and your fingernails bent and broken)... it's not gone Silicone leaves an insidious, powerful, invisible, soaked-in oil behind that will prevent any future paint, caulk, etc. from adhering properly. Just mention silicone around a car body/paint shop, and watch the pitchforks come out.

Okay, in case you can't tell, I'm not a fan of silicone

The thing is, if it were a case where there were no alternative, well, okay, we'd just have to suck it up and use it. But there are alternatives. Good ones. Excellent ones, even! And then you never have to end up on that garage floor, cursing and nursing those bent and broken fingernails.

I often wonder what it is about silicone that attracts so many people. I know that oftentimes it's because someone had recommended it (store clerk, mfgr), too. Maybe it's that clear, bouncy, jiggly "Knox Blox" seeming "goodness"? The opaque caulks seem less virtuous somehow?

Okay, whew, back to work

Raya

[HerseyBA]

"somewhat familiar with houses and cars. But not skyscrapers, etc. (I know "structural" silicone is used to put large glazing panels on skyscrapers, for example, but I can't speak to it.)"

My background for a number of years. Always plenty of RTV samples kicking around the lab.
Thanks for your info.

[Raya]

Skyscrapers? Heh, that's funny (because I used it as an example).

I don't do rockets either

Raya

[Ken C]

I don't know if this helps anyone out but the scamp owners manual says use silicone caulk. I don't know their reason behind this. Good luck.

[Raya]

Yep, and that's one reason why many trailers end up with silicone on them. I will resist commenting further, but I don't believe it's a good recommendation.

[Ken C]

Trillium echos Raya's recommendation, acrylic sealer not Silicon Here

[Francis McDermott]

Hey, thanks for the great information, Raya!

The point about bedding is critical for reducing leaks, I need to go there.

The chart posted gives good descriptions of several product families, I've tried a calk from Wurth which is incredibly tough. I'll post the name after I go find the tube.

The one good thing about silicone sealers is they have almost always been just spooged over top of the component or flange. When the removal, prep. and re-bed procedure Raya describes is followed that oily residue is mostly away from this bedding area.

FM