Tina, I'm surprised at how little many Painters know when it comes to Caulk, and as one colleague recently told me, "if you see a Carpenter with a Caulk Gun in his hand, take it away from him." Here is the issue: Almost all Caulk has Plasticizers. These plasticizers are what cause the flashing. It has nothing to do with your type of paint, other than the problem being exacerbated by flat paint, where the problem shows up even shinier. The other problem with Flashing is that it collects dirt, which in turn collects Mold or Mildew. Now for the solution: You should always use a caulk that does not contain plasticizers. Some of these are: DAP Elastopatch, DAP Alex Flex (available at most big box stores. If you have a PPG (formerly Glidden or ICI Dulux) near by, they have a product called Top Gun 400 that will do the trick. Custom products also has an Elasto patch (they actually got bought out by DAP but retain the Custom label). These Caulks will all do the trick. Unfortunately, Sherwin Williams doesn't seem to carry any Non-flashing Caulk, Be prepared to spend a little more, as this type of caulking tends to for some reason be around $3.75 or so a tube (at the time of this writing - at least where I live in Hawaii). One final word, do not confuse "Elastopatch" with Elastomeric! Many Elastomeric Caulks contain Plasticizers, even Daps 230 series. Never use Silicone. You can't paint it at all (and yes, I do know about the exception being Paintable Silicone). If anyone wants to verify the info I'm giving. Call DAP and ask to speak to a specialist and they will tell you the same thing.

Nigelsgarden -- Thanks so much for the link -- those look just like my units!! LOL. This is the second room I've done and I am getting bolder about disassembling what I can and painting those separately (especially the end caps, the facing pieces and the connectors). I am not bold enough to take the master wall housing off. Plus, they have been painted pretty much in-place before and are very, very sharp to handle. And now -- I've caulked some in place. (Oh well). Mine don't look as 'new' as the ones in the article but pretty darn close. My use of the long-end vacuum attachments and my steamer have been great. Plus, I've painstaking brushed everything viewable. I have a few more to go in this large room I am doing so I may just disassemble the next two units and see how it goes. Thanks so much! I may just spray the undercarriage lightly for good measure if I can't get that master housing off. Thx again!

It took me maybe 2 hours if that long to do the caulking on 3 walls -- I wasn't trying to fill the v-grooves, just fill larger gaps in joints in this 66 year old paneling. I agree with satin -- I just think painted paneling looks right with a little sheen, but you don't want a really shiny finish on the ceiling. Eggshell even might work -- I stopped using Behr eggshell a few years ago because they changed the formula and it had more of a sheen than I liked on the wall. I will try to get a good picture. It is a very gloomy day today so hard to get a clear photo of the details.

Way too many variables to say there is one correct way. Dozens of doors a week are painted here. White shaker MDF center panels all are caulked. It's done minimally, it's cleaned up and it's sprayed with water based 2K Italian. Never a problem they go all over the county. A factory solvent based finished would never be caulked. Not compatible. I couldn't even tell someone what grit to sand with without experienceing the product they are using under the same conditions. Too aggressive a grit with not cured paint you will have a mess on your hands. Other scenario you could not take it down enough and wont realize it until you respray and it return somewhat. A good sander will make the job much easier. I would spend the money on a Festool ETS. you would sand all the flat areas with that and the detail (corners, molding) by hand.