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Varnish adhesion problem

varnish adhesion

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#1 River Rat

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Posted 06 September 2016 - 01:35 PM

I've run into a finish problem I've never seen before and could use some advice.  I'm making a couple of 7wt bamboo rods and have gotten to the varnishing stage and there are fairly wide streaks, generally along the corners on the blank, where the finish does not look like it's adhering.  I used the same glue (Epon), sanded the raw blank to 320 grit as usual, wiped it down with a new tack cloth followed by DNA and varnished with Helmsman using a drain tube.  I did not see the problem after the first coat when I lightly sanded the entire blank.  There were several days between the first coat and the light sanding so I know the varnish had cured.  After the first coat had cured I used a manicurist file such as the Sand Turtle Gleamer but coarser rather than sandpaper to go over the blank and wraps followed by a wipe down with a tack cloth and DNA before applying the second coat in the drain tube.  There was a day or so between the wipe down and second varnishing.

 

My first thought was somehow silicone had gotten on the blank but I can't see how that would have happened unless the silicone was in the tack cloth which does not make sense to me at all.  Does anyone have any idea what happened and how I can keep from happening again?  I had hoped to stop at two coats for the tips but i imagine I'll have to varnish again to cover up these streaks.

 

Thanks,

Cliff


Cliff Parmer

If it's worth your time to do, it's worth doing to the best of your ability.


#2 BGreer

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Posted 06 September 2016 - 02:46 PM

That's a problem that pops up from time to time.

 

There are a lot of theories behind why it happens. Contamination is the biggest suspect.

I've not used a tack cloth, so I cant comment on that. I don't know if they are manufactured with anything on them.

I think wiping down with DNA is the best way to go. Acetone can leave stuff behind when it evaporates.

 

Some people say that having too sharp of apexes on your rod might contribute to the problem.

 

Some people add Penetrol to their varnish to help with the problem.

 

Maybe take a look at your drain rate also. That may have an effect if the drain is too quick.

 

I really don't have a definitive answer, but maybe some of this may help.

It sucks to put so much time in a rod and have varnish troubles.

 

Brian



#3 John T.

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Posted 07 September 2016 - 07:20 AM

FWIW, I use coffee filters (lint free) and DNA for wiping down blanks.


John T.

 

 

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#4 Tim Anderson

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Posted 07 September 2016 - 09:10 PM

When something used to work and now doesn't, you often need to look at anything that has changed.  A new tack cloth ... probably the culprit.

 

As for wiping down varnish, I prefer to use paint thinner (not the new milky stuff).  DNA can soften varnish and is often used to remove old varnish when restoring a cane rod.

 

Tim



#5 John T.

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Posted 08 September 2016 - 07:05 AM

Good point, Tim.  I was referring to graphite and fiberglass.  Coffee filters leave no lint.

River Rat, some good advice here.  Seems like it might be a process of elimination.  Any scraps for practice to determine the exact cause?  Good luck and let us know what you find.  Don't build bamboo but always like to  have the information.


John T.

 

 

Marriage is like a deck of cards- in the beginning, all you need is two hearts and a diamond.  In the end, you wish you had a club and a spade.


#6 fishbum

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Posted 08 September 2016 - 03:04 PM

Forget the wipe down with anything. No alcohol, mineral spirits, tack cloth or anything else. Wash the rod down with Warm water and Dawn dish washing detergent using a clean sponge kept just for the purpose for washing rods. The one I use has a scrubbing pad on one side of it. Rinse with warm water and hang to dry. While the rod is drying get your varnish concoction ready. Before touching the rod again, go and wash your hands in the same warm water and Dawn and rinse well. Dry your hands  with with a towel that was dried on a clothesline, not a dryer where fabric softener sheets might have been used. Varnish away.

 

Good luck,

 

Jerry



#7 Galt

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Posted 10 September 2016 - 11:51 PM

Following the above advice should eliminate contamination as the cause of the problem. If the problem persists, could it be that the finish is not receiving a complete scuffing? Flat sanding sticks are great for flattening 'nibs' and leveling high spots, but may not be covering the entire surface. synthetic steel wool (000), I find, works well for scuffing all of the surfaces. It can reach under guides and flow over wraps. It can even soften the sharp vertices, helping the finish to flow over them. Since polyurethane finishes have been notoriously poor at bonding to themselves, it is very important to give an aged surface a complete scuffing.

 

Something else to consider is that since these finishes cure from the surface inward, scuffing the surface exposes semi or un-cured finish to the atmosphere. This should be good for adhesion of a second coat. However, If the entire film was not fully cured at the time of scuffing and then was left for a few days before re-coating, that scuffed surface would then become a 'new' cured surface with the same limitations of adhesion and need for scuffing It would seem prudent, then. to re-coat shortly after any scuffing.

 

Galt


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#8 River Rat

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Posted 18 September 2016 - 05:46 PM

Thanks for the suggestions guys. 

 

To complete the post, I soaked some 0000 steel wool in acetone and let it dry.  Then I worked the rod over with the oil-free steel wool, wiped it down with DNA and applied another coat in the drain tube.  The coating appeared better in that there were only a couple of spots that looked like they didn't get coated very well.  The drain rate was 2" per minute with 12 minute stops at the top of a wrap, bottom of the guide and again at the bottom of the wrap.  When I was cleaning up the spots in the finish I found out that the coat was very, very thin.  The varnish is Helmsman and it has been out of the can about 14 months kept in Stop Loss bags.  I didn't notice any unusual gelling when I poured it through the filters into the tube and the viscosity seemed about normal.  I'm still baffled but figure I'm not going to get a better finish and so I applied a coat of carnuba wax and declared it finished.


Cliff Parmer

If it's worth your time to do, it's worth doing to the best of your ability.




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