Silicone Caulk Greasy?

[stan]

I've got sort of a specail project going where I put the caulk on something about the size of a half-dollar coin.

Imagine putting a small bead on the coin's face, then spreading it around with your finger. What happens of course is the caulk fills in and covers the small depressions while the higher area's (like the president's face) you can see still see because your finger sort of "squegees" it off.

Now if I let the caulk cure on the coin for 24hrs what should I find on the president's face? I would think nothing but there is actually a greasy residue which I did not expect.

This is 100% silicone:

I rub a blue colored old T-shirt on the raised area's of the coin and it comes away darker like it was wet or greasy (even after 24hr cure). If I put a small bead of caulk on a piece of paper (without smearing it) and let it cure, it looks and feels rubbery like normal caulk with no greasy residue, even if I pull it away from the paper.

Any thoughts on how this is occuring?

[George]

Likely the acetic acid that was liberated during the curing process attacked the metal. There are other formulations that are not peroxide cure that will prevent that.

[stan]

Ok thank you for educating me. The label for for GE silicone II caulk says the curing process releases Methanol and Ammonia but I think that's not any better. To add some more detail, this is actually an electronics application but I just used the coin as an example of the surface. The caulk/sealant will touch solder and a silver based paint (85% silver) which need to remain un-corroded and electrically conductive.

I may need some type of electronics grade sealant but it has to have a service temp of -40C to 110C when fully cured. Here are some things on my short list:

star brite liquid electrical tape:

dow corning 744

dow corning 3140

[David L. Martel]

Stan,

The coin analogy may be instructive. You know that coins are dirty and greasy after they have circulated for a while so why do you think the grease is a function of the caulk? So, what are you actually caulking and why do you believe that it is clean? I suspect that you are seeing a residue of crud from your coin that has reacted with the acid of the caulk in some way.

Dave M.

[George]

You are looking at the right stuff. Those Dow RTV products are specifically designed corrosion sensitive applications. I think the 744 is likely the most appropriate one for the use you described.

[Kuskokwim]

GE had some bad batches of clear silicone caulk that was oily and didn't always dry properly, but it was Window & Door not the Kitchen & Bath that your link leads to.

[laugh_insurance_sales]

If he kept his caulk in his pants it would not get greasy !!!

----- Free Laugh Insurance Inquire within !!!!

[stan]

It's kind of a small curcuit board with solder balls. I think the ammonia reacted with the solder during the cure process and that is what I thought was grease becaus it made the rag darker when I rubbed it. Probably was just solder that got softened up. This is the first time I've tried to use silicone sealant with electronics so I learned something new. I read accounts of amatuer radio hobbyists who have experienced the same issue. Thanks.

[Reed R]

Where did you learn about this bad caulking? I'm experiencing oily residue dripping from areas on the exterior of a metal building that were caulked several years ago and need to know more. Please reply - Thanks!