Problem with CA finish on curly koa

[aronson]

Hi all,

Turned a Sierra barrel a few weeks ago and have made several attempts (unsuccessfully) at using CA finish. All seemed well until I got down to the micro mesh pads. Somewhere along the way the finish would develop what looked to be an air pocket underneath the finish. The farther I moved into higher grits the worse it got. I sanded the barrel down to wood and reapplied anywhere from 3 to 8 coats of medium CA each time (without accelerant) and the same would happen.

Anyone ever heard of this? Is there an oil in the Koa I should be aware of? Something else I'm not aware of? I've had no problems with any other wood except this one.

Thanks!
Adam

 

[Pens By Scott]

Do you have any pictures?
I've had this problem in the past, what was happening was that I was sanding back into the wood. Doing a wet sanding with MM, it looked like a dull patch of CA, couldn't figure it out.

What I did to correct this, back then was using Russ's procedure for CA/BLO, i applied more coats (12), and let the blank sit longer (5 minutes or so) between coats.

This really hampered my production efforts, so I went to the Accelerator method, and have had less issues over all.

So, what worked for me was, more coats, more time between coats.

 

[Timbo]

I've finished several curly KOA blanks using CA without any problems, so I don't think there are problems finishing this wood in general. I can think of a few possible causes.

Old CA...but you say you don't have a problem with other woods so this is probably not it.

Contamination on the blank...did it have a sealant on it. When you sand it down next, try wiping it down with acetone or DNA before applying the finish.

Heat...if you're sanding at high speed, or using a lot of pressure you could be generating enough heat to affect the CA bonding. Try wet sanding. Don't forget to first seal the ends of the wood tube with thin CA to prevent water penetration.

Don't give up. Good luck.

Tim

 

[aronson]

Doing a wet sanding with MM, it looked like a dull patch of CA, couldn't figure it out.

Indeed, Scott. I don't have any photos. I took my frustration out on the tube after the n-teenth time sanding down and refinishing. :biggrin:

Contamination on the blank...did it have a sealant on it. When you sand it down next, try wiping it down with acetone or DNA before applying the finish.

Heat...if you're sanding at high speed, or using a lot of pressure you could be generating enough heat to affect the CA bonding. Try wet sanding. Don't forget to first seal the ends of the wood tube with thin CA to prevent water penetration.

Tim, I think you might be on to something... however... I had the same problem today with a block of Amboyna burl that I was able to finish a few weeks ago without any problem. With that blank I didn't seal the ends (I never had but thanks for the suggestion!) with CA but I did use a little beeswax to make removing the blank from the bushings a bit easier. I haven't been using acetone or DNA to wipe down my blanks before applying finish but I have been using mineral spirits. Could this be my issue?

Thanks again to both of you for your help!

Adam

 

[Grizzlyss]

Koa and CA Finish.

I found that you need to put 2 or 3 coats of thin on first, to provide a base for the finishing CA to go on to. Koa sucks up medium CA like a sponge I have found, and this stoppped that problem. I also clen my blanks with 99% pure rubbing alcohol and allow 30 seconds to dry before I apply any finish. I have also used both BLO and tung oil to pop the grain before I start with any CA and seems to bring out the grain and curly very nicely. Good Luck, and have a great week.

Sheldon