Well I am not too inclined to name the product that failed here because of a couple of considerations:
1) The product is a well known brand of RV Caulk in the industry with a good name and track record.
2) The manufacturer is quick to say ‘If you are applying over an area that has had silicone you MUST remove all traces of Silicone or our product will not adhere.’
I was just about to go back with the same stuff for the fourth time. I don’t get too excited about doing the same thing over and over and having it fail each time so I was dragging my feet. I began cleaning off the old caulk. This time I used an aerosol solvent ‘Acrysol’ which really did a great job of removing all the old solvent based caulk.
There were 6 joints that needed to be made ready.
The product I was removing would look great for about a week or two after application then it started to separate from one side of the joint. Also, as it was curing the solvents would gas out and these bubbles developed and made a real ugly looking joint in addition to the separation. It was a total fail on sealing anything and it looked terrible.
As many of you know we are in Southern California and when they say ‘it never rains in Southern California’ I believe them and am glad this is where I was when I decided to re-do this job this time.
This pic shows the seam with all of the solvent based caulking removed. There is none of it left but there does appear to be some silicone from a prior application. Silicone is very hard to get rid of once it has been applied. I used the Acrysol and a bunch of razor blades but it is virtually impossible to remove all the old silicone and nothing else will adhere on top of silicone except silicone.
So I decided to contact a trusted Mobile RV repair mechanic (Doug Garnett) from the Barkley Lake area back in Kentucky. Emailed him pictures of the problem and asked for his recommendations. Doug took a look and after a few questions and answers he said to try Dow 795 Silicone. ‘It will remain more flexible and stick on top of old silicone’.
Well I tried to get Dow 795 at all the local stores over in El Centro, CA. Home Depot, Lowes, Ace, Sherwin Williams, you name it. None to be found.
So when I got back to the computer, I did a Google search and a bunch of stuff came up. I looked for the link that would get me to the folks at Dow and what do you know, there is a live chat option.
I began a chat with them and sent pictures etc. Told them I was cleaning with Acrysol and the joint was looking clean and ready for new caulk. Told them the unit was a Carriage Cameo Fiberglass and the slide seams were bordered with painted aluminum next to the fiberglass panels. Tech support at Dow said that would be no problem for their product, it would work!
Now this is looking like a major big home run. Tech support added that as a final cleaning prep I should use Isopropyl Alcohol just before I apply the new Dow 795. They said 95% of the failures they see are due to poor prep and cleaning.
Enter technology: We are living in a time that has the potential to make life so easy and yet sometimes in spite of that I shoot myself in the foot. e.g. my four tries at sealing these joints in the past two years. I am also one that fully embraces the computer and uses it to my best advantage, but I have to admit, on occasion I am either a slow learner or old habits are hard to break. Could be too that I am a member of the club that thinks ‘if all else fails read the directions!’ Read on…
I clicked the still open Google search window to look for where to get three tubes of Dow 795.
There it was, AMAZON has it!!
Yep Amazon, and we have a prime membership so no minimum for free two day shipping. COOL BEANS
So with a quick few clicks I had three tubes headed our way! With a renewed vigor I went outside to do some more cleaning and getting ready for finishing this project.
The day came and I masked off the joints using blue painters tape and cleaned one last time using Isopropyl Alcohol. Then I began shooting Dow 795 Silicone into the joints.
From the second the first little bit of this product came out of the end of the tube I knew the problem was solved. It applied more smoothly and more evenly than anything I have ever used before. It tooled more easily also and the finished product looks great. The vinyl graphics show a bit of wear from all the removal of old caulk but the seams are sealed. It has been a couple of weeks and it is with high confidence that I can say this is a long term correction.
The bottom line: The warning for not applying over old silicone should have been something I paid more attention to. Live and learn as they say. I was pretty sure silicone had been used on the rig by someone and at the time did not give too much consideration to the warning from the manufacturer about silicone.
I hope this info helps someone and believe me there is a difference in Dow 795 compared to what you can get at the local hardware store.