The humidity here in Hattiesburg, Mississippi was around 100 percent. We got 3.5 inches of rain.
I did not have anything going on and decided to check out and set the pressure adjustments on my new Accuspray 19c. I had some old (6 months) 2-pound cut shellac that had a red stain in it and decided to use it to test my new sprayer as I made the pressure adjustments. I sprayed a scrap sheet of thin plywood during the adjustments and to check the spray pattern. After getting the settings to my satisfaction, I decided to spray a piece of walnut just for the heck of it. All went well, but in areas where I got the coverage a little thick, I could see some blushing.
I am really a newby at finishing. I know that high humidity will make shellac blush and I know that shellac has a short shelf life. I made the shellac from flakes about six months ago. I would be reluctant to use it on a fine piece of furinture and I would not attempt it when the humidity is as high as it was today.
I would like the answer to three questions:
1. What is the general humidity level at which one could expect to have some problems with shellac blushing?
2. After disolving flake shellac in DA, how long would that shellac be good to go on good work?
3. Does the cut affect either shelf life or blushing.
BTY, I spent some time running the catfich out of my garden it was so wet!
Replies
>>>1. What is the general humidity level at which one could expect to have some problems with shellac blushing?
It's hard to give a definative answer but most finishes begin to develop problems when RH exceeds 85-90%.
>>>2. After disolving flake shellac in DA, how long would that shellac be good to go on good work?
Again, can't say for sure but six months is about it. Date any you mix up. Try it on a scrap board and if it dries as fast as it should and is hard after 20 minutes, it's OK to use. But, it's always safer to use fresh material.
>>>3. Does the cut affect either shelf life or blushing.
In my experiance, shelf life is not affected by cut. But blushing is the trapping of moisture under the finish caused by the cooling from evaporation of the alcohol. I rarely spray shellac so I can't answer about the cut affecting blushing.
Thanks Howie,
From about may to October, the humidity in my area is hardly ever below 80-85.
The shellac I used was around 6 month old. I stirred it and saw a lot of "floaters" that were translucent. When I sprayed it on the walnut, I laid it on fairly heavy and I had no indication that it was near sagging, but where I overlapped and got it thicker, I saw the blushing. I know there are other good finishes but I really like shellac.
Thanks for your reply.
I don't know about avoiding blush when spraying shellac, but with lacquer, you can avoid the problem by adding a retarder. It slows down drying just enough to avoid trapping moisture in the film.
I would urge you to get some nitrocellulose lacquer to experminet with. I have sprayed it successfully in MN when it was both hot and very humid.
Thanks nikkiwood. I intend to try it.
Breeze, this is way off topic, but your post brings back memories. I used to work for Pillsbury, many years ago, and we used to use Hattiesburg as a packaging test market...because it was the worst place in North America when it comes to the shelf life of cake mixes.
...If our packaging could stand up to Hattiesburg, it could make it anywhere. :O)
Jon,
It's like the NY,NY song, If you can finish it in Hattiesburg, you can finish it anywhere.
Hattiesburg and the South is a really good place to live-if you can get accustom to the heat/humidity in the summer.
Thanks for your off topic reply.
Cool
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