Official Luthiers Forum!

Dear Experts,

I understand the principle behind blushing but apparently not how to get rid of it. I will start off by saying this is only guitar #3 for me and only the first using a spray gun for finishing.

OK, so here’s the story:
1. Applied a very thinned wash coat (3:1) with McFaddens vinyl sealer
2. Applied McFaddens clear grain filler
3. Applied a thinned seal coat (2:1) of McFaddens vinyl sealer
4. Applied 1:1 McFaddens Nitro – BLUSHING appeared
5. Applied 2:1 McFaddens Nitro + a tiny amount of retarder – blushing STILL there (see pics below)

From this site, I am under the impression I use the retarder as needed but in VERY small amounts. So did I just not use enough retarder, and need to spray another coat with more retarder? Do I need to sand down to the wood and start over? If this is the case, from what point do I start over?

HELP!!!

My sincerest thanks!!

Greg

I think that you need to deal with the humidity, not add more retarder. I have never had blushing in 5 guitars sprayed, but the relative humidity is at the 40 to 45 % range that I keep my shop at. There are temperature and humidity ranges that will allow real good spraying conditions.

If you spray again in proper humidity the blush already there should go away as the new coats will blend into the old allowing the moisture to come out. If it won't you may need to spray one coat with a lot of retarder to get it out, but as long as the humidity is high you will get this again.

Fred

_________________
Fred Tellier
http://www.fetellierguitars.com
Facebook page http://www.facebook.com/pages/FE-Tellier-Guitars/163451547003866

What Fred said, also this can be cause my moisture in your air line, even if the humidity is OK. I have these filters at my gun, even though I have a clean dry air supply.
http://www.amazon.com/Grip-Inline-Air-Spray-Filters/dp/B001PB841K/ref=sr_1_4/183-9460111-2229931?ie=UTF8&s=hi&qid=1252855703&sr=1-4

Its cheap insurance.

_________________
I didn't mean to say it, but I meant what I said.
http://www.brackettinstruments.com/

apply/ shoot a straight coat of retarder ' it'll take the blush out

Applying a straight coat of thinner will remove the blushing. Using retarder straight might be overkill.

This is not caused by moisture in your air lines. That will result in a different kind of problem, not unlike fisheyes.

Where is your make up air coming from? Directly through a door or window?

Are you thinning your lacquer? If you are shooting unthinned lacquer, it may be drying too fast.

I didn't think what I saw in the photos was caused by moisture in the air line, but a inline air drier and filter is needed for the best results.Remember to make sure they can handle the air volume that the spray gun requires otherwise you create other spraying problems, don't ask how I found out.

Fred

_________________
Fred Tellier
http://www.fetellierguitars.com
Facebook page http://www.facebook.com/pages/FE-Tellier-Guitars/163451547003866

First do nothing and watch it for a couple of days. If it is moisture blush, it may go away (although it is pretty severe).

Is there any white fuzzy stuff on the surface? That's a different kind of blush and has different solutions.

What are you thinning with? If it is from the hardware store, it may be your problem.

I'd recommend against ever shooting straight retarder.

What is the temperature and humidity where you are spraying?

_________________
Howard Klepper
http://www.klepperguitars.com

When all else fails, clean the shop.

Thanks everyone!!

Let me try to answer everyone’s questions thus far:

I spray in my (non-temp/humidity controlled) garage. When I sprayed yesterday it was probably around 80 degrees and 80% humidity. I’ve read the “15 point difference between temp and humidity” rule so it retrospect I should have been using the retarder for the first coat. It’s just that others on this forum have scared me in the use of retarder. The next day with relatively low humidity is Thursday and they are calling for around 71%. Will that be OK?

I am thinning the lacquer at 1:1. I am using “Klean Strip” brand lacquer thinner that I purchased from Woodcraft that says “Medium drying”. I use the same brand for my naphtha too. Is this brand OK?

There does NOT appear to be “fuzzy stuff” on the surface. It still feels very smooth to the touch.

Thanks again!!

Greg

I've always used the same brand thinner as lacquer. I also think the humidity was way too high. I'd recommend getting some Mcfadden thinner.

Another note, even though you're spraying outside you still need to protect your lungs. Wear an approved respirator. (you probably are, and may have already said so, but safety is important)

_________________
I didn't mean to say it, but I meant what I said.
http://www.brackettinstruments.com/

from what you have described, I would have to say that is definitely blushing caused by humidity.

unless you are under some severe schedule I would wait until you have more favorable conditions...the 'ideal' lacquer conditions are 70° and humidity below 50%...

retarder is an iffy chemical, all it takes is a case of using too much and having a finished product that never really hardens to learn that lesson...that being said, there is a valid use for it with the associated cost being a lengthening of the time it takes the lacquer to fully harden...because of the associated risks of the chemical I would suggest using a retarder that is specific for that lacquer and using as little as possible to achieve the goal of no blushing...

from my experiences lacquer thinner is lacquer thinner...with a catch...sure, almost any thinner will work to reduce the stuff and make it more easily sprayable, but many times the exact formulation of the stuff will be specific for best results with a given lacquer...because of what I'm sure are a combination of EPA rules and 'demand' (by painters who usually prefer to use the cheapest product available as opposed to a quality product which gives better flow out) I've been finding it very hard to find decent thinners around lately of 'generic' manufacture (which are usually far cheaper)...hell, even my local Sherwin Williams outlets don't carry quality Sherwin Williams reducers, rather sell stuff that is some crap that smells nasty and dries way too fast for my tastes...if possible use the manufacturer's thinner unless you are forced to do otherwise...

I've only had blushing occur once, and that was actually caused by temperature as opposed to humidity (I was up all night spraying a wet bar and hadn't noticed the temp had fallen to nearly freezing...I mean I knew it was cold, and was resorting to the trick of heating the cup in a pan of hot water, but not that cold)...I sprayed 2 coats of thinner only on the affected areas and that got 95% of the problem resolved...the part that wouldn't rectify I had to sand out, since I was still at the stage of color toning seal coats I wasn't too put out by the setch....

Throw the Kleenstrip thinner out and get a quality lacquer thinner. Sherwin Williams makes a good one and is what I use. I had some Kleenstip thinner and threw it out based solely on the color and feel of the product.