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Building Tips and technical articles. => Paint and finishing => Topic started by: Dennis Toth on September 11, 2020, 06:10:20 PM

Title: Clear dope stored in metal cans goes dark amber?
Post by: Dennis Toth on September 11, 2020, 06:10:20 PM

I have a question for the group about clear dope that has been stored for some time in sealed metal cans going dark amber in color. The dope seems to work fine, flows out nice and dries solid. I had some other dope from this same batch that I had in a glass jar that sat on the shelf just about the same amount of time and it is only straw colored. Both were about 7yrs old. Anybody come across this with clear dope? Could the cans be reacting with the dope giving that darker color (almost like it kinda rusted and dissolved into the dope?

Best,    DennisT

Title: Re: Clear dope stored in metal cans goes dark amber?
Post by: kevin king on September 11, 2020, 10:16:30 PM

I can only say I've never had an issue with Sig Light Coat turning rust. The other brand I have is rust colored.  But I can always use that for building up the substrate before the color, then never buy it again.

Title: Re: Clear dope stored in metal cans goes dark amber?
Post by: Dan McEntee on September 12, 2020, 09:53:11 AM

Quote from: Dennis Toth on September 11, 2020, 06:10:20 PM

I have a question for the group about clear dope that has been stored for some time in sealed metal cans going dark amber in color. The dope seems to work fine, flows out nice and dries solid. I had some other dope from this same batch that I had in a glass jar that sat on the shelf just about the same amount of time and it is only straw colored. Both were about 7yrs old. Anybody come across this with clear dope? Could the cans be reacting with the dope giving that darker color (almost like it kinda rusted and dissolved into the dope?

Best,    DennisT

     It sounds like you decanted it from a larger container? If so it may be the can you put it in. I think they treat the inside of the can with some kind of coating to prevent the can from rusting and that may be what you see?
  Type at you later,
  Dan McEntee

Title: Re: Clear dope stored in metal cans goes dark amber?
Post by: Norm Furutani on September 13, 2020, 11:30:41 AM

I’m pretty sure its rust. It gets worse in partially full cans (more air). Once a can is opened, I store the remainder in glass jars with PTFE seals (McMaster Carr). Tried HDPE jars/bottles and they crack over time.

NormF - 60+ years, sniffing dope