Heat resistance of finish built of multiple types

[decibel]

OK guys I have a question and I don't think I've seen it in Flexner's book but I could be fibbing as I haven't picked it up in a minute

My first project ever was a walnut kitchen table and it was a sad affair (imagine learning to use your jointer / planer on a kitchen table for the first time). The finish I used on that version of the table was a water based poly and it was somewhat thick. It resisted all the abuse my wife threw at it with hot items and cups. I later redid the tabletop once again out of walnut but used a different finishing schedule as follow all coats were sprayed with HVLP gun:

2 coats orange shellac

2 of tinted blonde shellac

3 coats of gloss Arm-R-Seal

2 thin coats of satin Arm-R-Seal.

Now here my problems. First off she dropped something hot liquid on the table and it literally burned a hole through the film. I can see it's shiny underneath which looks to be the gloss ARM-R-Seal. I'd say this happend probably within the first week of use so maybe the finish wasn't at it's ideal hardness. The real problem stems from she placed a hot container from the microwave on the top. It crated small pin like bubbles in the finish. I've also noticed I can get a white ring in the finish pretty quick in this version of the top as well.

Anyway my question comes down to am I having the heat resistance problems of the shellac? I'm not sure if finishes follow the "weakest link" theory and I will have greatly reduced heat resistance because of that. Secondly maybe I didn't tick enough coats of poly down? I brushed the previous top so it had a much thicker coat (but too thick) and armor-r-seal is really a wiping varnish so it's already thinned out so perhaps I didn't put down enough poly?

[AceHoleInOne]

How proficient are you at spraying? Usually someone new to spraying finishes tend to spray to thin, because fear of runs? Did you thin the first 3 coats of poly? Did you wipe any back? By doing so you reduce the film thickness, requiring more coats.

My gut is telling me you probably don't have enough build of poly on? Arm-R-Seal has high solids and is formulated for those type of conditions. Make an effort to use hot pads (can even make some out of wood and cork, bounus project and more shop time ) Finishes are heat resistant to a point...not totally heat proof.....Also you are correct, your finish probably had not fully cured.

-Ace-

[decibel]

How proficient are you at spraying? Usually someone new to spraying finishes tend to spray to thin, because fear of runs? Did you thin the first 3 coats of poly? Did you wipe any back? By doing so you reduce the film thickness, requiring more coats.

My gut is telling me you probably don't have enough build of poly on? Arm-R-Seal has high solids and is formulated for those type of conditions. Make an effort to use hot pads (can even make some out of wood and cork, bounus project and more shop time ) Finishes are heat resistant to a point...not totally heat proof.....Also you are correct, your finish probably had not fully cured.

-Ace-

Ha ace you got me! It was my first project spraying with the HVLP I could have probably laid down a thicker coat on the 3 coats of gloss but I'd still say they were almost a good wet coat. Now the the 2 coats of satin on the top were super thin. So if I didn't build the poly enough should I have built more with the gloss and then the satin? Should the satin topcoat be a nice wet coat a well. I worried about clouding the finish so I just put down enough satin to get the sheen where I wanted it, wasn't sure if that super thin coat was causing me grief as well?