CA and woods

[jd99]

I had a issue where the CA was dull in spots and polished up fine in others, and I'm not sure why.

Maybe it was one of those woods that doesn't take CA that well; not sure.

Is there a list some where that tells what wood not to use CA on?

Be helpfull for us newbe's

Thanks
Danny

 

[PenMan1]

You'll get hundreds of answers here and without having considerably more information, each answer could be correct.

My first GUESS would be remaining moisture in the blank. Oily woods (cocobolo, olive wood in particular) are very finicky about taking a CA finish.

My first ritual (since one of my yellow socks disappeared in the dryer and I forgot some of the words to the required chant) is to clean each blank with 3 "very wet" applications of CA accelerator after final sanding and before applying CA finish.

When PRACTICAL, I try to wait for 24 hours after sanding/cleaning before applying finish.

I hope this helps, but the causes could be numerous!

 

[OOPS]

When faced with an oily wood, a friend of mine places the turned blank into a cylinder filled with isopropyl alcohol. Thirty minutes in the bath takes out a lot of the surface oils that cause problems with CA.

 

[wiset1]

This may be an obvious question, but how many layers of CA are you putting on and what thickness?

The reason I ask is that if there's not a thick enough layer of cured CA built up and you run through the pads you may run the risk of wet sanding through the layer of CA in some spots which would give you high gloss in some areas and dull spots in others where the sanding went a bit beyond where it should have and hit wood surface. Take a close look to see if this is the case.

 

[PenMan1]

When faced with an oily wood, a friend of mine places the turned blank into a cylinder filled with isopropyl alcohol. Thirty minutes in the bath takes out a lot of the surface oils that cause problems with CA.

I did use alcohol, but found CA accelerator much more efficient .

When you think about isopropyl alcohol, there are two grades available.
90% isopropyl (hard to find, here), which is 10% water and the more common 70% isopropyl which is 30% water.

Depending in which Accelerator you use (acetone base or naptha base) there is less water. To my simple mind, less water means less chance of ADDING MOISTURE to the blank.

Respectfully submitted.

 

[SteveG]

What Tim just said. In the big picture, sand thru on the CA finish is the MOST common cause for symptoms you experienced. It takes very little time to remove or sand through the layers of CA you worked so hard to apply! If the CA did not go on well, you are that much closer to the "sand thru". Some times it is a combination of multiple causes, such as the possible moisture problem.

 

[jd99]

I tried a couple of things, even sanded it down to wood twice, the first time I had maybe 5 -6 coats the next time I had 10 - 12 coats each time the same thing and the dull spots were in the same place every time.

The pen was for me, so it's not a big deal, I will try the accelerator trick next time.

First time I had this problem and I'm sure it's not the last.

Thanks
Danny

 

[leehljp]

Are you using a mandrel? Have you checked the bushings with a caliper to see if the hole is off center?

Tail stock just a smidgen too tight on the mandrel; bushings with a .003 off center hole, a bent mandrel with runout of .003 on one end. Using the original tail stock center instead of a 60° live center can cause this. Sanding with just a smidgen too much pressure while using a mandrel will do the same. There are other circumstances that cause this too. And the result will be one side in one spot will be sanded more than the rest of the blank.

And I have just mentioned the mechanical-techincal aspects. Not the ones mentioned above of moisture, oil, CA etc.

From my experiences in reading here - more times than not, the problem is that there is not enough of a buildup of CA before sanding. A slight out of center or out of round can still be overcome and not noticed if the CA build up is enough that you are not sanding through. Still if you are having high spots that are sanded though to the wood, I would look for the cause.

 

[Jim Burr]

I've had this happen on a few occasions. What usually works...for me!! only!!...is knock it down a bit with 0000 steelwool, give it 3 good coats and make sure you're not applying additional heat. Knock that down one more time and see what happens. Add one more for shine or leave it for matte. I did this earlier today and it still works!

 

[SSobel]

I was letting a friend turn a pen and as she was finishing it, she got too close with the accelerant and didn't let it dry. As she applied a new coat of CA, it left spots. Just another couple pennies to toss in.

 

[jd99]

Jeezze.... this CA stuff is tough :wink:

Up until now my CA finishes have been fine, course i havent done a lot, but it's all part of the hobby. :biggrin:

I just keep the ones that don't work for my self, :wink: if anyone ask if i have a pen, I just say yea sure here is my case with 20 in it pick one.... :biggrin:

Thanks
Danny

 

[Pariss]

For oily woods I have always used Metholated Spirits on a paper towel to wipe over the spinning blank. Leave to dry for 5 minutes, then do your CA finish. Never had any problems. It also cleans all the dust and dirt off the blank. Surprising how much crud is actually left on a freshly sanded blank. Just have a look at the paper towel after the wipe over.