I recently applied polyurethane to a bowl and after waiting 36 hours it still has a little bit of a tacky finish. I was wondering if anyone has tried baking on a finish to get it to cure out and if so at what temperature.
Greg
Technically, that would work. In reality, you're in for a seriously stinky kitchen for an extended period and food may never taste the same.
Factors that can affect cure time are humidity, temp, UV, and cure time for that particular finish. Also, some woods such as cedar that have high turpentine content can slow or stop the cure.
Putting it next to the furnace in the basem*nt works relatively well, though, once again, you get the stink factor.
Dietrich
You didn't include the brand/type of Polyurethane finish you're working with but, typically, Polyurethane needs to be somewhere between 50 degrees and 140 degrees fahrenheit to dry properly. However, the humidity can dramatically affect the drying characteristics so you also need to factor that into the equation. Frankly, I wouldn't count on proper drying at the low end of the temperature recommendations. I'd want to work in the region of 70 degrees as a starting point. I would not recommend trying to bake on the finish. Oven drying can be both tricky and dangerous. Finishing pieces in an oven usually means the exterior (the wet finish) gets warm more quickly than the workpiece. That can cause the finish to dull, bubble, etc. More importantly, fumes can flash over into open flame easily, especially as the workpiece warms and the solvents vaporize.
Greg,
When I'm working with Mirror Coat epoxy I slow spin the turning on the lathe and put clip on desk lamp about 8" over the turning. The incandescent bulb warms up the turning and allows it to cure.
Personally, I'd stay away from anything with an open flame or that might directly blow air onto the piece. The first for flammability (this finish may not flame, but another might and I could forget). The second for all the dust I'll have to rub out of the piece.
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Thanks for the replys guys. It was a minwax spray bomb poly that I used. I guess what happened to it was that my shop was to cold and wet when I sprayed. It was about 50 and raining that day maybe colder. It then dropped to below 40 which I have since been told poly doesn't like.
Against better judgement and the wife wasn't home to stop me I tried drying it last night in the oven. The oven only goes down to 170. I wished it would have gone down to 120, it would have made me felt better about the experiment. I now know that this will work. Fumes were not to bad, she didn't notice when she got home. I sat in front of the oven and watched it the entire time because I was afraid of burning the house down. About every 15 min I would open the door to touch the edge to check temp of wood and state of finish. It took a little over 2 hours but it is done. I am going to make a hot box for my shop out of a freezer so that I don't have to do this again.
I am not saying that it is safe to do this in your oven at home. I do not recommend it in anyway. This is just what I did. It is dangerous and could lead to a divorce.
Greg
electric oven use
Our electric oven houses a full time pizza stone. On cool / humid high days I heat up the oven or follow up after the oven has baked / roasted something. Make sure you turn off the oven and once everything has cooled down to 100 degrees (with oven light on full time), place the item to be dried into the oven. To reach that optimum temperature it may require opening the door a few minutes at a time. I can maintain 100 degrees F for days without reheating the oven. Keep the light on! Humidity is very low.
Also, might want to hang a sign on the oven, DO NOT USE!
Just remember, guys, that you need air flow and that the fumes put out by the drying eurythane are both
toxic and flammable. Best off finding a warm spot in the basem*nt or making that hotbox with the freezer (with vent holes in top and bottom to allow convection).
Dietrich
Here in sunny warm South Florida we have Indian Rosewood the doesn't let Poly dry well. It takes 21 days, three full weeks, unless we wipe down the bare wood with mineral spirits then set it in front of a fanfor a few minutes. Then a light poly coat, immediately to fan again. Usually dries in 10 min. Then two more thin poly coats with fan dry. After that we sand 400 - 600 grit. At this point any futhur poly coats dry normally. Many of us just switch to deft (not over the poly) since it dries if a few minutes.
As an enthusiast with a deep understanding of woodworking and finishing techniques, I'd like to address the issue of a tacky finish on a polyurethane-coated bowl. The individuals in the provided discussion are seeking solutions for curing the finish properly, and I can offer insights into the factors affecting the drying process and the various methods discussed by the participants.
The original poster, gdc, applied a Minwax spray bomb polyurethane in unfavorable conditions, with low temperatures and high humidity. The first responder, dkulze, rightly pointed out the impact of environmental factors such as humidity, temperature, UV exposure, and the specific cure time for the chosen finish. Furthermore, the type of wood used can also influence the drying process; woods with high turpentine content, like cedar, may slow down or even stop the curing of polyurethane.
GeorgeH emphasized the recommended temperature range for proper polyurethane drying (between 50 and 140 degrees Fahrenheit) and warned against attempting to bake on the finish. He highlighted the potential risks of oven drying, including uneven heating, dulling, bubbling, and the danger of solvents flashing into open flame.
Brickey shared a technique involving a clip-on desk lamp with an incandescent bulb placed over the turning on the lathe when working with Mirror Coat epoxy. This method utilizes gentle warming to facilitate the curing process without introducing potential hazards.
The original poster, gdc, also experimented with drying the polyurethane-coated bowl in an oven at 170 degrees Fahrenheit due to the cold and wet conditions during the initial application. While he successfully achieved the desired result, he acknowledged the risks involved, including toxic fumes and the potential for a dangerous situation.
Other contributors, such as bob elliott, suggested using an electric oven with a pizza stone to create a controlled drying environment, maintaining a consistent temperature for an extended period. This method, while effective, requires precautions to ensure safety, such as turning off the oven, maintaining low humidity, and warning others not to use it during the process.
In conclusion, the discussion provides a comprehensive overview of the challenges and potential solutions when dealing with tacky polyurethane finishes in woodworking. It underscores the importance of considering environmental conditions, wood type, and safe curing methods to achieve the desired results without compromising safety.
