Question
I am a decorative artist and mural painter and presently we are finishing a wonderful library in a private home. The finish is executed over a lacquer primed MDF raised panel room. This includes built-ins and wall paneling and crown mouldings, (basically top to bottom). The prep work in a fast paced construction site was such that all of the base coats on all elements are unknown. To avoid any material problems I have prepared the room and sprayed a high grade acrylic semi gloss warm grey paint.
The first and second "strie" or dragged finish is in alkyd glaze pigmented into a deeper warm grey. The first pass (horizontals) is thinned slightly with mineral spirits and penetrol for open time. The second vertical dragged pass is a lighter than base coat glazed grey alkyd producing the final "linen" effect.
I want to achieve a mirror like finish over this and we have turned the entire room into a cross draft spray booth that is filtered and well warmed. My chemcraft supplier has given me two options Acryllak 95 high gloss lacquer but warns that all oil based paint must be completely dry. The second is Nitro "old school" Lacquer.
My concerns for both are 1: the water born Lacquer adhering properly and being sandable and buffable. I have had this stuff peel off in sheets off of alkyd before. It’s possible that it was not completely dry in that scenario.
2: The reaction of Nitro Lacquer over such thick alkyd coats of glaze. Also, the ability to build the Nitro thick enough to cover any ridges left by the faux finish resulted in too many coats and inevitably cracking. Any help would be very much appreciated!
Forum Responses
(Finishing Forum)
From contributor C:
You can answer your own questions by first making up a sample and testing it out to see what the results will be.
That said 1: Nitro will yellow extensively over time and ruin the original appearance - if yellowing is a concern then I would tell you not to go that route.
2: Your choice of alkyd glaze medium could have severe repercussions, many alkyds are reactive especially to coatings solvents, which could cause lifting, crinkling, and other problems. They dry by themselves ok, but form a barrier to adhesion with many clear-coats. Many of them also yellow badly with time, though I’m not saying yours will - there are literally hundreds of different kinds of alkyds.
3: From where you’re at now the best thing to do is make a sample with every step you use and test it for adhesion and get a 300a UV lamp to check for yellowing 100 hours under this lamp will show 1 year in direct sunlight. This will tell you how the finish will look in a year. 1000 hours is equal to 25 years exposure, and so on.
For you - each step from this point on will need samples to test every step to know for sure the outcome - unless you want to remove the glaze medium and start over - not an easy task and I don’t know your deadline - hope it's not short.
I would not go water-base over alkyd normally - too much chance of adhesion problems. You would be much better off with a high gloss acrylic solvent type, but you still need to test for adhesion problems to do that correctly you need to let the clear-coats dry for 30 days at least - do you have that type of time? If so - then I would recommend Delta labs 525 series of gloss acrylics but still test for adhesion - as I said if it’s a reactive alkyd it may cause problems.
I have a few more questions, Is there an oil based high gloss finish that can be polished to that sort of lacquer mirror like sheen? I generally spray Benjamin Moore low luster 1hour on oil based finished furniture in our booth here in the studio and love the product as it has a nice mellow feel. The yellowing properties will be fine in this application due to the warmth of lime stone and sandblasted oak flooring (herringbone pattern).
The main concern and initial reason to use lacquer was that high gloss mirror like finish. I have never had the need to polish the gloss varnishes before and have only done to date, final off the gun finished final coats with those products.
In an ideal scenario I would be looking for a fairly quick drying high gloss oil based
varnish that could be prepped for a final spray of that ilk. Perhaps there is an oil-based sealer that could be done first and sanded to achieve that final surface for a very high gloss finish.
It seems as if your faced with using a product that is compatible throughout each step - that product is oil based. Oil based coatings don’t dry very fast.
The real problem started with my desire to have that soft linen finish and I do wish I could have used water-based glazes but the open time is not enough.
The workability for my specialty paint finish needs to be quite long and would be impossible to achieve with water-based glazes because of the size of some of the central raised panels. Anyone know of a sealer that will be higher slack and clear as a bell that is oil based?
Waterbornes with ammonia in them burn into the shellac; other waterbornes may require a 320 scuff sand of the Sealcoat. We have used gloss to build up thickness and then topcoat with desired sheen. We have found that Polyvar by SDA works well for complex jobs that you seem to be tackling. If you are new to waterbornes, this would not be the job to experiment on.
I will not be sanding the final glazed faux finish. So in order to protect all the work thus far I will have to get a get a good couple of solid and well covered coats before even a light scuff coat will begin. I am willing to lay a lot of material on over the next few weeks. Water sanding to approximately 1500 to 2000 grit before the rubbing compounds come out. I am in awe at my luck to have stumbled into this breadth of knowledge!
