ca finish shrinking

[Robert Taylor]

abount nine months ago i made several stamp pens. i turned wood (pine) slightly undersize then glued the stamps on and covered with two coats of modge podge. they they were lightly sanded and finished with about twenty coats of thin ca. while setting up fo a show this past weekend i noticed cracks in two of the pens. a closer look revealed that the finish not only cracked but shrunk by about 1/16" on one end and about 1/8" on the other. i have no clue as to why.

 

[bad]

It's very hard to give an opinion without actually having the pen in hand. With that said, I'll do exactly that . I would suspect the wood underneath first. If you've had a significant change in humidity, like say, going from winter to spring, then that COULD cause the wood to expand or contract.

 

[greggas]

If the shrinkage was in the entire blank ( I cannot tell from the picture) then i would agree that the wood shrunk

 

[Russianwolf]

CA is plastic and ain't going to move that far. The wood has expanded. Pine is more susceptible to this kind of movement than many hardwoods. But I will say that I'm shocked that the expansion wasn't radially also and splitting the finish along the length of the pen.

Check the brass tube inside, if it's short of the end of the blank by approx. the same amount, then you know its the wood, if its even with the wood on both ends still, then it's the finish moving. brass ain't going to move that much either.

 

[Robert Taylor]

in the first picture the extreme left side has shrunk about 1/16", in the second picture the right side has shrunk about 1/8". the crack goes about 2/3 of the lenght. the pen in the rear of the photos has identicle shrinkage and crack except that the crack is now open about 1/8" all the way to the stamps. the pine under the stamps is construction grade 1 by scraps. the pens are stored with about 200 others with various finishes including ca and are stored where there are no extreme temp changes. the wood is still even with the end of the tube. if the wood had expanded enough to crack the plastic/ca finish i suspect it would have tore the paper of the stamps which it did not. i am totally clueless as to what happened here. the last picture shows the open crack.

 

[Andrewsignore]

i wonder if the stamps absorbed some moister before they were sealed in and then dried and shunk slightly and causeing the ca to crack leaving the void

 

[SteveG]

Wood is always subject to dimensional instability, and the degree of that varies by type of wood, grain direction, moisture content, etc., and other variables. Environment can have significant impact on those variables. Your process of applying the stamps likely aggravated the situation. Pine is often not seasoned (dry) when purchased. CA is (as far as I know) dimensionally stable. So you would probably do well to select a different substrate wood fot this type of pen. Hope the next ones work out better!

 

[nativewooder]

There appears to be a wrinkle in the stamps under the finish and that makes me think, as other say, that the wood was not dry, but is now.

 

[Robert Taylor]

what appears to be the wrinkle is just reflection of light. the finish is no longer smooth though. i think any future stamp pens will be cast in resin with the stamps glued to the tube.

 

[Sawdust46]

If you used construction grade pine scraps particularly from Hompe Depot or Lowes they have a high moisture content. For detail work like pens if you are going to use that kind of wood I would recommend you invest in a moisture meter so you can determne the "dryness".

 

[Curly]

Even if the wood was dry wouldn't the water based modge podge make the wood and stamps swell a little as they absorbed the water? If there wasn't sufficient time for them to dry again that CA finish would wrinkle and crack as the blank dried and shrank in the months after. What puzzles me is why the CA pulled away from the ends of the blank as the stamps and wood didn't. Does the modge podge shrink as it dries? Two problems causing the failure?

Pete