REFLECTOR: Scratch Test

[Keith Hallsten]

Phil,

 

I think your questions show that you have a pretty good understanding.  The
point of the scratch test is just to demonstrate that the epoxy actually
hardens, as opposed to remaining "gummy".  Just take a chisel or nail or
some other pointy tool and verify that the leftover epoxy in the cup is
really hard by scratching it.  It's qualitative, but you can tell the
difference.

 

If you aren't sure that the epoxy still hardens like it did before, get new
hardener.  It's not worth the risk if the hardener has really gone bad.
That said, it's probably OK if it's less than 3 years old!!

 

Keith Hallsten

Slow builder 

 

  _____  

From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Phil Hooper
Sent: Wednesday, July 06, 2005 8:51 PM
To: 'Velocity Aircraft Owners and Builders list'
Subject: REFLECTOR: Scratch Test

 

Collective.

 

1.	Can someone explain how to conduct and evaluate the scratch test?
My hardener crystallized, and I'm in Southern California.go figure.  It's
only 9 months old.  I placed the jug in hot tap water and it went back to
solution with no problem.  I have done a small lay-up with three layers of
bid, and left some in "the pot".  In 24 hours, how would I check it...see if
it scratches with 36, dig at it?
2.	It has been suggested that older hardener can be diluted with
denatured alcohol.  How do you evaluate how much is enough?  Is it sound
practice?  When it gets to the stage that it needs dilution, I wonder
whether it would be worth a trip to Spruce.15 minutes from here.  44/100
sounds pretty precise to me.
3.	It seems like the main resin will last a long time.  It is the
hardner that ages, and that the styrene vapors out of the bottle.  Is that
correct?

 

As you can surmise, I'm a slow builder.  And just for a little patriotism
after the 4th (and some pride), I've attached my excuse that lives 329 miles
to the north, born April 15.

 

BTW, sorry for the ignorance and thanks for the help.

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