Self-bubbling Dicor

Almot wrote:
...snip...The DICOR link says "if membrane has black backing, it's EPDM, and if it's solid color through than it's TPO". It is "solid" black color all the way through EXCEPT for white surface, which is painted....

All RV rubber roofs are white on top otherwise the sun would heat the rig up too much. You may have a paint on top done by a prior owner, but it would have been white originally from the factory.

Again don't worry about it, just give the bubbling time to settle down.

Thanks, John&Joey.

The DICOR link says "if membrane has black backing, it's EPDM, and if it's solid color through than it's TPO". It is "solid" black color all the way through EXCEPT for white surface, which is painted.

So I phoned RV manufacturer, they have no clue other than material is "Dicor gray roof" (sort of gray-ish shade, to me it looks white).

Then called Dicor, they only could tell that if it is a Dicor material, than Dicor lap sealant will work no matter whether it's rubber or TPO. For competitor's roofs the choice of Dicor sealant does mater (i.e. Lap sealant or Ultra sealant), but for Dicor roofs they said it doesn't.

Oh well...

I think you're doing a fantastic job. I also think the Dicor is chemically bonding to the rubber roof creating the outgassing thereby the bubbling you're seeing.


If you want to be nervous about something then verify that Dicor can be used on your type of rubber roof.

Clicky on Dicor

Thanks again.

About "clean, no chalk surface" - this exactly is the problem. The paint on EPDM roof is aging from the day one, leaving chalk-ish powder on the surface that can be picked up with any wet or even dry rag. Solvent just dissolves more paint, after removing most of chalk - and also removes oil-ish residues, if there are any.

My roof had this chalk of course. Everybody I asked, had same calk on the roof. I felt that this caulk would affect the adhesion of sealant, and tried to remove it very thoroughly - water with a drop of dishwashing liquid, then lots of clean water, then solvents. Cleaned areas became very smooth after this, and spider-like web pattern emerged - this is black rubber starting to show from under white paint.

And, no matter how many times I rubbed it with clean water after soapy water - the rag still picked up some traces of white stuff. The ultimate test was packing tape - when it didn't pick up anything white, I considered the surface clean.

FWIW, I never use solvent. I just use a good hand scrub brush and some spic and span/water in a bucket. After that a thorough rinse with clean water. Wait till the next day in the early afternoon to go back up.

I'm sure solvent is a good thing, but on the other hand maybe not(back to petroleum and maybe overkill?) What you want is a clean, dry, no chalk surface, I think I get that with just a good wash. So far I've haven't ever had a problem. YMMV

Your temps are perfect for what you are doing. Be carful not to get in a hurry in the morning, and let that dew fully dry and the rubber to give up any moisture that it may have. I know it isn't suppose to absorb, but after the dew is gone feel the sunny rubber part then a shaded area (behind the AC.) I swear it will feel cold and damp.

Also those low temps will make it take even longer to cure. As in more the 48 hours.

John&Joey, thanks. Leaving it alone and getting off the roof for a week is probably the right recipe, at least for my nerves :)

Do you wash it with water first, to remove dust, and then with solvent, or just hit it with solvent?

How hot - last few days it was 18C = 64F. Probably 70-80F on the roof surface when there is no wind. Plenty of sun. Dew, yes. Early morning temps are 4C = 40F.

How I do it is I wash the area the day before. Then about 2-3 pm the next day I apply the Dicor. This allows any dew to be dry and any dampness to be long gone.

Don't know how hot you're dealing with, but what I do is on the TX/MX boarder by Brownsville/Matamoros.

LEAVE IT ALONE! Don't be pricking those bubbles you'll only compromise what you painstakingly did. The very best thing for you to do is stay off the roof for a week and enjoy life. After a week go up and admire your work which should last for up to 10 years before you need to retouch.

Thanks people.

Here is my findings after experimenting, 24 hours after applying.

On aluminum: no bubbling with either Methanol or Paint Thinner.

On wood: no bubbling, and solvents were not used of course.

On EPDM roof:
Very little bubbling after Methanol.
A little more bubbling after wiping with just water.
A bit more bubbling after Paint Thinner, - surprise.

Again - this is 24 hours after applying, and I applied it about 15 minutes after cleaning.

Meanwhile, 3 days old Dicor (photos show it when 24 hours old) has shrunk some.

What nobody tells you is that Dicor cures VERY slowly. You won't see it on the can. In FAQ o their website it says 80% cure after 48 hours. Geocel cures fast, similar to most caulks. What bothers me - even though Dicor has shrunk some after 3 days - when I tried and pricked a few bubbles, there was nothing but air underneath, and tiny spot of the clean roof surface. No soft matter of uncured Dicor.

I suspect that roof paint releases fumes after cleaning. Possibly - more so after Paint Thinner than Methanol, as PT dissolves more paint, I could see this on the rag.

Q: How long do you people let it dry after cleaning on a warm sunny day, like 68 in the shade (God knows how hot on the roof, the sun is hot here in Mex).

Old/bad tube is a possible reason too. Far away from civilized world with Camping World Cabela etc, I have 2 choices now: to proceed cautiously, letting it dry 30-40 minutes before Dicor, or to postpone the whole project until next winter when I'll bring another tube of Dicor or Geocel, or both.

That's normal for Dicor to do that. It has petroleum in it, but it evaporates quickly. Give it a full week and the bubbling will be gone.

Best time to use Dicor is on a nice sunny warm breezy day. This will help it cure faster and reduce the amount of bubbling.

BTW, the wet finger thing is just fine. Everything you did is great, just give it time to fully cure. Report back in about two weeks.

I'd just wonder why you mixing 2 types of sealants. I'd R&R the brackets w/ Dicor.
I mounted all solar brackets w/ Dicor, after cleaning w/ P thinner, never a problem. The only thing I hate about Dicor is its slow curing, but that's what makes its durability and longevity.