sanding goo

[circus]

Sanding gooy urethane primer surfacer. Cost a fortune in clogged sandpaper. Any brands out there that are sandpaper friendly? Tackless

 

[Rod (NH)]

Exactly what product are you talking about so others can avoid it? I have never experienced anything like that using PPG's OMNI <a href="https://buyat.ppg.com/refinishProductCatalog/ServeFile.ashx?FileID=b37c7bd9-42a7-49e1-937e-ca8ea22d43bc">MP182</a>. That product always sands very easily w/o clogging, at least for me.

 

[Howard H.]

I was kind of wondering what the rest of the story was, too...


Howard

 

[glennster]

sounds like hardener was not added to the primer.

 

[circus]

MP 182 is the culprit. Use to work, must of got a bad batch or bad hardener. What a mess.

 

[Patsdeere]

Might be worth just strippping and starting over. What a mess that I am glad I don't have to deal with.

 

[Cockbird_Hunter]

Was it mixed correctly? 5 (MP182) : 1 (MH165/MH166) & were both products new? The MH165/166 Hardener label indicates to use product within 14 days after opening. Maybe some others can suggest what maximum shelf life they have been able to "get by with" when storing the hardener cool/dry after initial use...

I plan on using this product for the first time this weekend over the MP170 epoxy on sheet metal parts. I chose the MH166 slow hardener based on experience learned from previous posts on this forum.

I will follow-up with the results....

 

[GordoSD]

How long did you wait after mixing, to spray it on?

Gordo

 

[Red Ford]

If urethane primer is applied too heavy it stays soft and gooey. Even when properly applied and cured it's a little that way. I know there are many who disagree, but I prefer epoxy instead of urethane.

 

[CNKS]

The urethane Circus used should not have that problem--and it is not a primer, but a surfacer, intended to be sanded smooth. It is not intended for bare metal, but is intended to be applied over epoxy, which is not sandable, or some other compatible primer. Been using MP182 off and on for about 8 years, it has always cured properly and could be sanded the next day. I typically apply 3 coats about 10 minutes apart, let dry, sand and apply 3 more and sand, that usually does it except for occasional spot treatments. Hardeners have a shelf life, the same can should not be used indefinitely. Epoxy catalysts have a much longer shelf life.

 

[CNKS]

I keep my hardener in a refigerator, after squirting a product called Bloxygen which displaces the air and supposedly acts as a preservative. Seems to work as I have used the same can for 2-3 months. Others have done nothing and used it for a year or so after opening, the procedure I use is so simple that I don't want to take the risk. Your MP 182 should be fine. It sets up in the gun or container fast. Max time before spraying is 60 minutes at 70 degrees, I try to use it in a few minutes, no longer than the coat every 10 minutes, or 3 in 30 minutes.

 

[Rod (NH)]

Ditto what CNKS said. MP182 does set up fast. That's an excellent point that needs to be repeated. The warmer the ambient temperature, the faster it sets up. You want to get the last coat on and get the gun cleaned without delay. Mix, spray right away and cleanup ASAP. If you linger too long, the stuff turns to jello. You don't want it still in your gun in that state. I had to hustle once to get the gun cleaned properly. I could tell that the gelling process had started by a noticeable, unexpected reduction in fan pattern (increase in viscosity) during my last coat. I am now more sensitive to timing with MP182.

 

[circus]

Must of been the old hardener. Luckly lacquer thinner removed the goo. A substitute hardener (Marhyde)seemed to work better but not perfect. Hope it eventually hardens after it's painted.

 

[Rod (NH)]

Mixing ingredients from different manufacturers can be risky. Why are you not using the appropriate MH165 or MH166 hardener as recommended? "Substitutes" and generics can be more trouble than they're worth.

 

[GordoSD]

I think the MSDS states you must wait 15 minutes after mixing to spray it.

Gordo

 

[Cockbird_Hunter]

Gordo:

That is true for the MP170 Epoxy Primer but NOT the MP182 2K Urethane Surfacer Primer

 

[circus]

Agree. It failed then I substituted. This time "by the book" didn't work.