CA-BLO problem

[tomwojeck]

All,

I've recently started finishing my pens with CA and BLO. One problem that I seem to have is that I have gotten blotchy marks inside the finish. I'm not sure if that's a good explanation, but I'm not quite sure how else to put it. It's not scratches, it almost seems a bit hazy in places.

Am I not letting it cure enough before polishing? Or is it the wood that I'm using? The pen I had the problems with was made of padauk. Maybe I'm putting too much pressure with the MM?

The actual surface is glassy smooth, but it's just a few hazy spots that I think are making an exellent finish just OK.

Thanks for your help!

Tom Wojeck

 

[fmunday]

Originally posted by tomwojeck
<br />All,

I've recently started finishing my pens with CA and BLO. One problem that I seem to have is that I have gotten blotchy marks inside the finish. I'm not sure if that's a good explanation, but I'm not quite sure how else to put it. It's not scratches, it almost seems a bit hazy in places.

Bummer [] I've never experienced it myself but I've heard others speaking of the this same sort of thing. The closest I've come to that is with a piece of Manzanita Burl into a Robusto pen. One section of the blank would not polish no matter what I did to it (before putting on the finish). I never did figure that out. I've seen similar problems to what you describe with flat wood projects and those always related back to touching the sanding sealer before it was completely dry or one of the varnish coats before dry. That seemed to me to be related to acid/oils from the skin interacting (in a delayed manner) with the sanding sealer/varnish. I've never seen it with poly finish. When I do BLO/CA I go directly from MM to BLO/CA with no wait in between. When applying BLO/CA I make one pass the length of the blank with a BLO saturated pad and apply CA immediately. When satisfied with the BLO/CA, I apply 1-2 coats of a padding lacquer used like a friction polish (Mylands, etc.) and then allow the blanks to "rest" on the lathe or mandril for 30 minutes to a couple of hours without touching them. Since I don't use a sealing step, I don't have to worry about contamination of the sealer.

Am I not letting it cure enough before polishing? Or is it the wood that I'm using? The pen I had the problems with was made of padauk. Maybe I'm putting too much pressure with the MM?

I would have to say that it depends on the polishing method that you are using but CA should cure to a hard surface in well under a minute. This time will vary some with the viscosity of the CA but the BLO seems to stablize the curing process allowing you to get a glass like surface. One tip is not to be stingy with the CA or the BLO. Use an amount of CA that seems right and then use 25% - 50% more. I've seen more problems from using too little CA than too much. Padauk is a hard fill usually requiring (my way) 5 - 6 BLO/CA applications but it doesn't give me any other problems with finishing. It is doubtful that you are putting too much pressure on with MM. It will get hot under pressure and you'll know if you've used too much pressure. It will melt sections of the MM surface. My son did that with the last pen that he finished. If your MM is still intact you probably aren't using too much pressure.

The actual surface is glassy smooth, but it's just a few hazy spots that I think are making an exellent finish just OK.

If the surface is glassy smooth then I would have to suspect some sort of contamination of sanding sealer, BLO or CA during the application. Review the steps you went through from start to finish (no pun intended) and see if you can spot any places where there might be a chance for contamination and then turn another pen and finish it paying particular attention to contamination possiblities (if any) that you may have discovered. Scott and Don Ward are also using BLO/CA extensively and they probably have better ideas about this than I do.

Thanks for your help!

Tom Wojeck

I'm not sure I was that much help.

 

[dw]

Tom,

Man, I'm glad you started this thread! I've had exactly the same problem...with CA by itself, with CA/BLO and even with poly (although less so and easily fixed). I even asked the same sorts of questions here and in the Yahoo group with little in the way of certain solutions.

I have gone through thinking it was oil on the wood, oil on my hands and blaming the BLO (I've had it occur with CA/BLO more often than with CA alone) to blaming the CA itself to thinking I needed to sand the blank better...to thinking it was an off center mandrel and these were thin spots in the finish.

My current theory is that I've been sanding with the lathe turning too fast. I don't know how fast you are running when sanding but I saw an excelleant explanation of the way (and why) heat builds up when you sand at too high a speed. And the CA <b>will</b> melt...or at least soften. Actually this last theory seems, in retrospect, to fit my experiences. And it seems to fit better with the fact that these "ghosts"...I like to call them...are neither consistant on the blank itself (like all on one side) nor consistant from pen to pen.

It may also explain why some folks don't seem to have any idea of what we're talking about. Either they aren't noticing these splotches or they aren't getting them. I prefer to think the latter.

In the end, it may turn out to be some combination of factors but the first thing I'd look at is how fast your blanks are spinning when you sand.

In passing, I, for one, would welcome...encourage, beg, etc....further input by anyone else who has experienced this problem or anyone else who even has a theory as to why this happens.

 

[Guest]

I just figured I screwed it up[^]

 

[wayneis]

I know what exactly you are talking about as it has happened to me twice. I was rather bummed out because the rest of the blank turned out great. I desided to experiment and tried using Hut Crystal Coat and it went away. I don't think that it just covered it up because it is clear but for some reason it was gone. It happened again last night, I made a Thuya Burl Woodworkers Pen from CSUSA. When I saw the ghosts (by the way that is a good way to describe it) I pulled out the Hut again and it worked again. The first time was with a walnut blank so it was different woods. I don't know why I got the ghosts and I don't know why the Crystal Coat would make it vanish but it seemed to work so I'll take it and run with it until someone can explain better.

Wayne

 

[Efletche]

I doubt this will help, but I did a couple with the MM and went to the CA glue. They too were hazy. I realized it was the very fine dust particles still on the pen surface. I resanded and before using CA again, took a surgical scrub brush and wipped the pens surfaces clean. Once the CA was re-applied, no more haziness. I don't know of this is helpful in your situation, but thought I would mention it.

 

[woodman928]

It sounds to me like blushing. That is when the humidity is to high and/or the finish is drying to fast its a common problem with high humidity here in Missouri. Not sure what you can do with BLO but in lacquers you can use a retarder to slow the drying.
Jay

 

[William Young]

Woodman928
You brought up a good point there about blushing for anyone that is using solvent based laquer. When I used to finish guitars in another life, blushing was a real problem when the humidity was high. Back then, WB laquers had not been developed yet. Now with WB laquer, the problem of blushing is a thing of the past. The product can actually be thinned with water.
W.Y.

 

[tomwojeck]

Originally posted by DCBluesman
<br />Just a couple of quick notes on this problem. First, I hope all of you are wiping down your turned blanks with a tack cloth after MM and before applying a finish. This is a must in all areas of woodworking. Also, use the tack cloth if you do any sanding between coats. Next, CA depends on moisture to cure properly. If you are sanding until the surface is hot, you have probably dried out the surface of the blank too much. Either sand lighter to keep the heat down or let the blank rest such that at least a little air humidity settles on it. That way the CA can properly cure.

From what you said here, I can see two problems that I might have:
1. I was just using a clean cloth after each grit of the MM to make sure it was clean.
2. I think I was too agressive with the MM, generating too much heat. I'm going to do another tonight to see if I can fix the problem.

Also, it's been very rainy and humid in the Baltimore area and my shop isn't air conditioned, so that could affect it too.

 

[NCTurner]

Tom and others,

I am not sure I completely understand what you're saying, but I do sometimes see a 'spot' on my finish, which mainly appears as I get to 3200 or higher MM. This usually is when I have sanded through the CA. There's really no way to feel it, as it feels, and when wiped clean, it looks exactly like the rest - glossy. However, as I sand, I see very small dust particles accumulate on those parts of the wood.

I may be the only person that does it this way, but I do NOT sand with the lathe on, after I have applied the CA. In my article posted on here (see below)

http://www.penturners.org/content/CAFinish1.pdf

I mention that I sand with the lathe off, after applying the CA. I have found it cuts down on the heat buildup, and does wonders for removing the concentric rings. It also is faster, believe it or not. I don't need to spend a lot of time on each MM grit.

I know some folks love the "BLO/CA" finish. Maybe I've not done it correctly, but I was not pleased with the pens I finished this way, and honestly, haven't been overly impressed with those I've seen finished this way by others. Pictures make it so difficult to really see the difference....it really does require holding them in your hands and viewing by eye sometimes, to see the minute differences. What I noticed is a slight bit of cloudiness in pens finished with the BLO vs. just the CA. An easy way to compare finishes is to simply do two different finishes on the same pen. The fewer variables you change, the easier it might be to isolate an issue, such as the "ghosting".

By the way, I did take a picture of one such "ghost".....it's the bocote pen in my album at:

http://f1.pg.photos.yahoo.com/ph/ncturner2002/my_photos



Hope this helps!