First Off: I am using Centari Acrylic Enamel 99A. Using Dupont's correct reducer 8022s and Dupont's correct flattening agent. I am however not using Dupont's 793s activator but rather but a universal acrylic enamel gloss hardener. The mix Ratio: 8 paint, 1 harder, 4 reducer ( So it sprays and lays out good ) I have been spraying auto paint since the 70's and have used a multitude of paint mfr's products from enamels to urethanes over the years. I have sprayed 99A ( Non Flattened ) many times and always get a consistent smooth, deep high gloss result ... and btw: better results with conventional then HVLP but can achieve good with either. My current problem is I flattened a new can of the 99A to the amount I wanted for flatness and sprayed in a controlled booth but after the last wet coat and in about 30 minutes small sparse spikes or nibs slowly begin to appear and after full cure out time vary sparsely throughout the sprayed surface area. This happens regardless if I filter, when I filter, how I filter and with what; when I add the flat to the paint and mix then add activator and reducer or any other of a number of passible combinations. I have sprayed back to back with the same gun, same booth, same conditions, same air and fluid setting, same compressor, same everything and mix ratio using flattened and non flattened test spray out test panels side by side within minutes of each other in the same isolated controlled areas. Results: The non flattened is consistent with no nib/spikes and the flattened has what appears to be sparsely randomly placed appearing nib/spikes. Even had my Dupont paint jobber flatten a test batch of Centari 99A. Sprayed this out and repeated the same and still got these nibs/spikes. My Dupont jobber told me 99A does not use a binder since it is an acrylic enamel as opposed to a s.s. urethane which uses binders. Apparently they too just mix the same flat agent as I use by just adding the flat to the measured out 99A after throughly mixing both the paint and the agent. They even used a new batch or flat agent as well. Upon spray out of this batch I still got these nibs/spikes. Mix Technique; Combining and stirring paint and selected flattening agent together thoroughly and have done it both mechanically and by hand. Used various forms of filters from 125 to 190 to the old sock method when adding the flat to the paint or when just adding the flat to the paint then when ready filtering that before activating and reducing the mix. Have also added and filtered the flat at the end after activator and reducer added and still get these nib/spikes albeit in various amounts throughout the surface. Therefore, I must conclude that one cannot flattened any given paint without these upon tack/cure nib/spikes appearing either oh so slight or in abundance. So if anyone has some illuminating technique or information that one can utilize to ensure a faultless flattened homogeneous spray out with a bench flattened acrylic enamel or a s.s. urethane I for one would very much like to hear about that method or solution. Oh and please I would like the discussion to stay topic specific of flattening enamels or urethanes not about using a particular spray gun or using a particular bc/cc product instead or to just flattening a clear coat and be done with it or comments that one is surprised that acrylic enamels are still used .... etc. - Thanks in advance
I have know idea why you would bother with acrylic enamels, and the answer to the question is what you don't want to hear. Completely senseless post.
I have only used flattener a couple of times and never had any problems with it. It was a universal product and I have used it in a couple of different makes of acrylic enamel but if I remember right I mixed the paint as I would for a gloss coat and then added the flattener to it. This post reminds me of what I've said before. No matter how many paint jobs I do it seems like I very often go "Damn I never saw that happen before"
It would be helpful to see pictures. I have painted cars for 30 years but admit to not having used acrylic enamel at all for over 10 years but used it quite a lot before that. My first thought of anything that slowly start to appear or grow in the curing process is a contamination of the sprayed material. Moisture making it to the spray gun will cause grief. Pounding on to heavy of coats and/or timing the coats to close together will cause little pop up buddies . Also while a freshly painted surface is curing if the solvents can’t escape because the air moving across the surface isn’t moving fast enough the air becomes solvent heavy and the painted surface will react unfavourably.This poor booth airflow can be caused by booth fan needing to be turned up or booth intake filters needing a change. You can also get problems if the booth air is to humid because the painted surface can’t gas off properly as the air is to heavy with moisture. I would carefully sand the nibs open and look at them closely with a magnifying glass.
Yes product gone bad could also give trouble. Can you see the nibs as soon as the paint hits the panel or do they kind of blister up? Could it be the surface underneath reacting badly with the topcoat? I’d like to sand them pop ups and see what’s inside. Like they say on the H.A.M.B. pictures or it didn’t happen.
I had that same problem, the flattening agent was old. I had mixed and sprayed it successfully about 6 months prior.
My experience is that the flattener has to be shaken extremely well before use and strained before adding to the color mix.
Not having used any since the '80's, I am not certain what today's flatteners are like, but what was available then, required this, because it was like a chalky substance, held in suspension, and would leave small globs of it behind when sprayed. Flattener was also one of the reasons I use a strainer on everything, and have a small screen stuffed in at the bottom of my gun cups, like the ones in the throw-away cups. There used to be one available for siphon feed guns also, that went on the bottom of the tube, but I have not seen one for a while.
I thank you all to take the time to respond ... If you read my post again you will find that my test panels were shot together at the same time, in the same booth, the same gun, the same mix etc ... just the panel with the flat agent reacts. All materials were fresh ... fresh Centari 99A and flat agent as my jobber made some up the same day using a new batch of 4515s flat agent and Centari 99A . In short this batch too responded the same as my material batches had done when flattened .... Each test panel was purposefully cleaned and then final wiped and tacked and sprayed at the same time under the same identical conditions .... so that pretty much rules out contamination, moisture, bad technique, poor non cleaned surfaces, wrong or poor filters, air piping, gun adjustments, equipment issues, spray environment etc. . When viewed under magnification it is not solvent pop or it would indeed appear as well on the non flattened test panels, which it did not. The flat agent used was mixed and applied at a base temperature of 78 degrees and was thoroughly agitated by hand for 4 minutes prior to dispensing into the thoroughly stirred and filtered paint. The catalyst and reducer are fresh. The spray out test batch was filtered before adding to the lone paint before addition of cat or reducer and filtered again prior to addition of cat and reducer and then filtered again into the cup. We sprayed using both our Binks 115 and our DeVilbiss SRI pro mini gun with complaint tip. Both guns sprayed both the non flattened and the flattened test panel true and flat. Two wet coats were applied. All additives used were Centari specific agents except the hardener which is the Universal hardener Super Wet everyone uses and which consistently works well as designed when activating an acrylic enamel. Since I too have been painting since the early 70's I know what fish eyes, solvent pop, dirt/dust nibs etc look like so pictures were not the first thing I thought about to post but I can do so as perhaps someone may see something with more experience then myself that 45 plus years of painting prevents me from deducing As I detailed earlier in my post I can only conclude it is the catalyst itself reacting and causing the flat matrix material ... i.e. most likely a particular size or type of talc used and the suspension medium it is in to react to the hardener. My next step is to use my magnetic heated stir plate with magnetic palette rod and let the mix of just paint and flat agent agitate over night to ensure complete assimilation. This would emulate what the paint manufactures do in canning out flattened enamel paints. It was my hope that perhaps one or two of you may have had the same or similar defects appearing in your bench flattened paints. I have experienced this in not only acrylic enamel but in single stage urethanes as well as detailed above. Just a pint of Centari 793s activator is very expensive and I want to rule out any and all other possibilites before purchasing the Centari specific 793s activator . Regarding post questions about the timing of the appearance of the nibs/spikes. They appear about an hour to 2 hours later. Acrylic enamel is designed to be applied wet with very little time between coats unlike an epoxy or a single stage urethane system. These nibs/ spikes are ice burg like structures when viewed under magnification and are integrated surface floaters that when the larger ones are carefully picked at to remove the crowns under magnification it appears crystal like and when colored sanded disappear with the disappearance of the flattened surface with when you color sand a flattened painted surface returns the gloss because flat agent resides in the upper crust of the painted surface thus enabling the talc or flat agent used to deflect the light. Solvent pop does not create crystal spikes and contamination such as dirt nibs most always resides beyond the out mil surface and goes as a rule down into the matrix of the paint mil layers. This phenomenon does not show case these types of specific defects. I will attempt to keep everyone posted as to my progress and any solution I come up with. Oh .... and The reason for using an acrylic enamel is project specific for my purposes at this time and there is nothing "senseless" about that. Old iron get off my cloud if you have nothing better to add then that. Your B.S. is unprofessional, discourteous and insults my craftsmanship, experience and intelligence.
The Jalopy Journal
