Troubleshooting Gloss Variations with a Post-Catalyzed Laquer

      Viewed from an angle, this finished piece shows some flat, dull areas where the proper gloss wasn't achieved. Pros try to diagnose the problem and suggest possible fixes. December 1, 2005

I sprayed some DanSpeed by Chemcraft. Straight on, the finish looks terrific, but when viewing the finish from an angle, with the light just right, some areas seem to be glossy, while other pockets look dull. The overall effect is blotchy. I can re-spray if needed, with HVLP gun, but would welcome some suggestion on how to get a uniform finish. Would sanding #600, #800, #1000 help any? Would rubbing out help, and if so, what compound would be best?

Forum Responses
(Finishing Forum)
From contributor B:
I spray this product all the time and to the tune of about 35 gallons a week. I've never seen what you're talking about. Are you using a pump to spray? Are you using the proper amount of retarder? Is the viscosity and temperature of the product being measured before spraying? These are all things that will affect drying times and consistent sheens.

From the original questioner:
Yes, I'm using the proper amount of retarder, the temperature is uniform, I'm using a HVLP and compressor. I'm not sure about the viscosity, though the finish on one panel of the cabinet is from the same batch and in some places it's rough and in others it is glossier.

I sprayed water-based aniline, but before I did so, I wetted the surface, let it dry and then gave it a fine sanding, but I'm wondering if what I'm seeing is grain raising at some points and not others. That could be affecting the light refraction. If that's so, I obviously gave it too light a sanding. Or it could be talent and skill with the actual spraying. I gave the cabinet a wet sanding with #1000 and boy, it sure is smooth to the touch now, but the problem is still there, though the sheen looks a little worse. So maybe I'll lay on another coat.

From contributor G:
If your finish is smooth, then it certainly sounds like a substrate issue. Posting your finishing schedule might help narrow it down. You didn't mention the type of wood you're using. Are you sure you are not just seeing the chatoyance, or "flip" in the wood? Does it change when you look at it from different directions?

From contributor B:
Danspeed has a characteristic that I forgot to tell you about. I mostly use satin and the flattening agent must be stirred at the bottom of the can. I don't know if this may be of some help, but basics need to be mentioned.

From the original questioner:
I appreciate the suggestions. Here's some more info: Maple plywood. The first coat went on thin and dry with the surface being vertical. Afterwards, I sprayed onto a horizontal surface. The mix was stirred. I sprayed another coat and the sheen has come back, but there is still splotchiness when the light is just right. I don't think it is chatoyance. When I get my eye level with the surface, it looks like there are high and low spots and the low spots have filled with Danspeed and the high spots don't have that same look of glazing. However, the plywood is level, the surface was leveled before I sprayed, so I doubt that it really is a pooling effect, because I sprayed uniformly over the entire surface. As I mentioned earlier, it looks great when looked at straight on. I'm wondering if that valley and high spot effect is the subsurface being telegraphed in some way through the Danspeed. Can raised grain really look that awful through the Danspeed?

From contributor G:
"thin and dry"

Been a while since I used DanSpeed and it's been reformulated since then, but I do remember that it is fast. The speed part isn't kidding. It can easily dry in the air on its way to the surface. Could it be possible your first coat wasn't a wet coat, or it dried on its way from the gun, then the topcoat showed the irregularities? You did sand between coats, I presume. Did you use it as self-sealing? That's my only other guess. Your Chemcraft rep may have some ideas.

From contributor M:
Are the flat spots only on the high spots? Is it very consistent this way? If not, is there a chance that there could be some moisture either in the product or in your lines? Was the catalyst fresh, material fresh? Maybe try some on a scrap of the same maple ply, sanded as you did before. How long did you let the wood dry before you sprayed?

From the original questioner:
The flat spots are only on the high spots. The plywood dried for about 6 months. I put on another coat this morning. Uniformly wet on a level surface so any part that inadvertently didn't get the same thickness of Danspeed should level out, because the surface is leveled. I saw the same problem, though a bit reduced. I'm using 10% catalyst, as per instructions. I'm wondering if the Danspeed sets before it can level itself into a uniform sheet. Could that be it?

From contributor G:
If it feels smooth, it is smooth. You'd be able to feel raised grain. Can you feel these peaks and valleys with your fingers? How large are they?

From the original questioner:
I can feel the difference between the rough and smooth areas. The smooth areas have a glossy sheen to them, while the rough areas don't have that glossy, glassy sheen. They aren't really rough, but they don't gloss over. Is that enough of a clue?

From contributor R:
I don't usually spray anything except a satin or semi-satin sheen, but on cheaper plys I've noticed knotholes in the underlayment telegraphing through the coatings. I've noticed this especially on a sealer coat, but once I have moved on to topcoating, the dull spots usually are gone. I forget what it's called, but if we do use a ply, the face veneers are on top of a 1/4 ply of MDF, whereas the rest of the ply is kind of like a Baltic birch. Since we switched over to this product, we haven't had this sort of problem.

From contributor G:
I'm having trouble envisioning all this. You had dull pockets, you wet sanded them smooth, you resprayed and you got splotchiness and roughness that you can feel. These are in the low spots, I presume. The high spots are okay. I'll also presume your gun settings are correct, proper atomization, not putting out too much product, etc.

Well, you've got enough lacquer on there you can do some fairly aggressive sanding without fear of cutting through. Use 320 - 400 good quality paper on a hard block (if hand sanding) or a ROS with a 3/32 orbit and a good flat pad and sand it until it's all smooth and powdered. If you get some low patches that the sandpaper doesn't touch, that would indicate the plywood is uneven. That could be the reason your scuff sanding after the wetting didn't cut down all the raised fibers, which could explain roughness in your valleys. Then spray an even wet coat, not too heavy. You could even add extra thinner to ensure it won't be too heavy. Don't let it pool in the valleys.

From contributor D:
Stirring does not get the flattening agent off the bottom of the can. As a Chemcraft distributor for 15 years, we recommend using a shaker. 8 times out of 10, gloss problems have been product that is not mixed correctly. The other two times it seems to be a viscosity issue. There are other factors - heat, humidity, and in bigger shops it is wrong temp on the ovens.

You said you use the 10 percent catalyst. You may want to use the slow thinner, this time of year. I think somebody also mentioned to thin your first coat a little bit more to make a sealer, which will help with your problem, also.

From the original questioner:
The can I'm using is less than a week old and I stirred the product. If it is a mixing problem, do you think another coat, with properly mixed product, would solve the glossing problem? Or would the already sprayed product hinder the glossing effect? I didn't quite catch the full meaning of your comment on thinning. Could you elaborate a bit, please?

From contributor D:
Which Danspeed are you using, the 424-44 Series or the 432-62 series? If you are using the 424-44 series, the cat ratio is only 7% by volume, which may cause the sheen problem, along with other over-catalyzation problems.

Danspeeds can be reduced with the thinners at 10% to 20% by volume. Most shops here use 10% thinner to get the product at spray viscosity. (The 424-44 series is 18-19 with a zahn #2, the 432-62 series is 20-24 with a zahn #2).

You can reduce the Danspeeds with more thinner to make a seal coat. Some shops go 50/50 product/thinner to make their seal coat, which shouldn't interfere with your total dry mils.

On a scrap piece of wood, try to create your problem again, then sand with 220, and recoat with properly catalyzed product (if you are using the 424 series) thinned out at 10% to see if your problem disappears. You may want to do half the board at 10% and the other half at 20% thinner to see which looks best.

The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).

Comment from contributor E:
When reading through I caught that you are sanding with a hard block. This is good for initial sanding, but if your plywood is not a good quality and has uneven spots you will just bridge over the lower spots. Try sanding with a sponge after your initial block sanding. This will form into the low spots and get rid of your grain raise.

Also you may want to talk to your plywood vendor about the grade and specifications you should be receiving. Also talk to your representative from Chemcraft about what thinner you should be using. From what I have read it smoothes out in spots so I would try the sanding first. Material will not flow in some spots and not in others if the initial coat is applied evenly and the sanding is good.

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