Official Luthiers Forum!

I've read a few posts in which people mentioned problems with Royal Lac when sprayed using a special formulation supplied by the owner, Vijay. I recently finished two guitars using the regular formulation straight out of the can. You'll see in the photos that both guitars show signs of crazing.

I emailed Vijay and asked if he had any thoughts on what may be causing it or if there's anything I can differently to avoid this in the future. That said, I don't think I'll spray Royal Lac. It's a really nice finish, so I may pad or French polish, but not spray.

[Edit - Since posting this message, the creator of Royal Lac helped me understand that my approach to using the product was probably the cause of the crazing. Scroll down to learn more.]

I've got a mandolin out there I sprayed with the normal formulation and as far as I know it is fine. But naturally I have some questions. How long has it been since you sprayed it? What filler did you use? Did you seal with Sealac? And, of course, did you hear back from Vijay?

_________________
Steve Smith
"Music is what feelings sound like"

In my experience you will always hear back from Vijay. So far the same day, great customer service!!!

cecil

Yep. Vijay is great. We've already exchanged a few messages.

My hope is this is a problem with my finishing schedule/technique and not the product overall. But I wanted to post it here in case others are finding similar issues.

I didn't notice crazing when buffing out the guitars. I buffed out the rosewood about 2 months ago. I buffed out the mahogany about 3 weeks ago.

I didn't take notes as I finished the guitars, so here's my schedule from memory. I pretty much followed O'Brien's schedule for padding (via his YouTube video), except I sprayed.


- Sand to 220
- Seal guitar with 1 lb cut of shellac
- Pore fill with AquaCoat - It takes many coats to completely fill the grain. I did this over the course of a few days.
- Spray 3 coats of 2 lb cut of shellac, 20 minutes between coats. (I used SealLac on one of the guitars)
- Let dry overnight
- Lightly sand with 400 grit to get it close to level but not totally.
- With both guitars, I sanded through.
- Spray 3 coats of 2 lb cut of shellac, 20 minutes between coats.
- Let dry overnight
- Lightly sand with 400 grit to get it close to level but not totally.
- Once I didn't have any other sand-through areas, I started spraying Royal Lac. 3 coats, at least 30 minutes between coats.
- Let dry for 3 days.
- Sanded until about 70% level. I think I used 600 grit wet (water)
- Sprayed a few more coats of Royal Lac, 30 minutes or more between coats.
- Let cure for more than 30 days
- Level sanded with water 800, 1000, then up through the micromesh grits
- Buffed with handheld buffer using 3M Rubbing Compound. Then swirl remover.

When I buffed the guitars, I didn't see any signs of crazing. It seems these started at appear 15-20 days after the 30 day cure time.

With the rosewood guitar, I sanded through during the final leveling. I scuff sanded, recoated with RoyalLac and waited the 30 day cure time before leveling and buffing a second time.

Your schedule is similar to what I used except no pore fill since I was working with maple, spruce and ebony. I'll have to get hold of the mandolin owner and check it out.

_________________
Steve Smith
"Music is what feelings sound like"

I've had sprayed shellac craze that I mixed myself from good ingredients. There are others with much more experience than me, but shellac just doesn't seem to tolerate thick wet layers. 3x sprays every 20-30min is nothing for nitro but I think 3 of 2lb cut that fast might strain even conventional shellac. Just my small experience.

Sorry we're going to school on you Mike.

No problem about getting schooled David. I'm here to learn. It sounds like your thoughts align with Vijay's. Here's his response...

++++

Hi Mike,
The procedure looks fine except with a few issues that have caused this defect.
A few basics before I go in to the details. I am sure you know these.
1) A film will crack if the elasticity or flexibility is compromised.

2) Films lose their flexibility if the molecular structure is not correct or disturbed. The bonding does not have chains with the result the molecular movement is hampered.

3) All films will cure faster when subjected to heat. If it is a single resin, it will self-condense and not pose a problem. If it is a combination of resins, each individual resin may self-condense leading to an inflexible film.

4) Crosslinked systems have a minimum of two resins. A backbone resin and a crosslinker resin. As solvent evaporates, certain molecular groups in the two start to bond and create a film.

5) All films are dynamic. There is always molecular movement. Easy movement give good flexibility.
I’ll list the issues as I see it;

1) The time in between coats is inadequate. Please bear in mind that you are spraying a 2lb cut mixture, which is 21% solids by weight. After 30 minutes, even though the coat looks dry, it has not gassed out far enough and ready for another coat. When successive coats are applied, they inhibit the gassing out of the previous coat. Hence the whole drying process gets delayed.

2) Level sanding after only three days introduces water in the system that is still curing. 70% leveling results in reaching the first few layers. Water further increases the dry time since it readily mixes with the solvent and slows the evaporation rate.

3) Next a few more coats are put on a surface when the existing film is still drying slower than normal. The new coats dry faster than the previous film and inhibit the gassing out of the previous coats. Therefore even after 30 days of cure, the first few layers are curing ever so slowly.

4) Lastly when a power buffer is applied, it generates heat that travels down to the lower layers and as mentioned above, the individual resins self-condense causing cracks. You MAY have avoided the self-condensing if it was hand buffed.
What would have been ideal?

"Once I didn't have any other sand-through areas, I started spraying Royal Lac. 3 coats, at least 30 minutes between coats."

3 coats in a day with at least 2 hours in between. I realize that this is more than required, but since it is being sprayed, it is a thicker layer than padding or French Polishing. So a bit more time is beneficial.

"Let dry for 3 days"

Yes, let dry for 3 days and hit it very lightly with 600 grit dry. Spray another 3 coats or more if need be.

"Sanded until about 70% level. I think I used 600 grit wet (water)"

This should have been done after at least 20 days. 70% leveling is removing a lot of the finish. Water goes into the first layers at this point.
Sprayed a few more coats of Royal Lac, 30 minutes or more between coats.

Royal-Lac thinned 50:50 and maybe two coats at 2 hour interval.
Note: It is best to avoid the 70% level wet sanding. This actually may be the main cause for the failure.

Your schedule would have been fine while using a pre or post catalyzed product. Since Royal-Lac is un-catalyzed, it takes longer to crosslink and cure.

+++




Sent from my iPad using Tapatalk

No problem about getting schooled David. I'm here to learn. It sounds like your thoughts align with Vijay's. Here's his response...

++++

Hi Mike,
The procedure looks fine except with a few issues that have caused this defect.
A few basics before I go in to the details. I am sure you know these.
1) A film will crack if the elasticity or flexibility is compromised.

2) Films lose their flexibility if the molecular structure is not correct or disturbed. The bonding does not have chains with the result the molecular movement is hampered.

3) All films will cure faster when subjected to heat. If it is a single resin, it will self-condense and not pose a problem. If it is a combination of resins, each individual resin may self-condense leading to an inflexible film.

4) Crosslinked systems have a minimum of two resins. A backbone resin and a crosslinker resin. As solvent evaporates, certain molecular groups in the two start to bond and create a film.

5) All films are dynamic. There is always molecular movement. Easy movement give good flexibility.
I’ll list the issues as I see it;

1) The time in between coats is inadequate. Please bear in mind that you are spraying a 2lb cut mixture, which is 21% solids by weight. After 30 minutes, even though the coat looks dry, it has not gassed out far enough and ready for another coat. When successive coats are applied, they inhibit the gassing out of the previous coat. Hence the whole drying process gets delayed.

2) Level sanding after only three days introduces water in the system that is still curing. 70% leveling results in reaching the first few layers. Water further increases the dry time since it readily mixes with the solvent and slows the evaporation rate.

3) Next a few more coats are put on a surface when the existing film is still drying slower than normal. The new coats dry faster than the previous film and inhibit the gassing out of the previous coats. Therefore even after 30 days of cure, the first few layers are curing ever so slowly.

4) Lastly when a power buffer is applied, it generates heat that travels down to the lower layers and as mentioned above, the individual resins self-condense causing cracks. You MAY have avoided the self-condensing if it was hand buffed.
What would have been ideal?

"Once I didn't have any other sand-through areas, I started spraying Royal Lac. 3 coats, at least 30 minutes between coats."

3 coats in a day with at least 2 hours in between. I realize that this is more than required, but since it is being sprayed, it is a thicker layer than padding or French Polishing. So a bit more time is beneficial.

"Let dry for 3 days"

Yes, let dry for 3 days and hit it very lightly with 600 grit dry. Spray another 3 coats or more if need be.

"Sanded until about 70% level. I think I used 600 grit wet (water)"

This should have been done after at least 20 days. 70% leveling is removing a lot of the finish. Water goes into the first layers at this point.
Sprayed a few more coats of Royal Lac, 30 minutes or more between coats.

Royal-Lac thinned 50:50 and maybe two coats at 2 hour interval.
Note: It is best to avoid the 70% level wet sanding. This actually may be the main cause for the failure.

Your schedule would have been fine while using a pre or post catalyzed product. Since Royal-Lac is un-catalyzed, it takes longer to crosslink and cure.

+++




Sent from my iPad using Tapatalk

Just to follow up on this, Vijay's response is very helpful. I have a better understanding of how the finish works and how I can improve my process. My guess is that it's not the product by how I used it.




Sent from my iPad using Tapatalk

That's a great response from Vijay and I appreciate you sharing with us. My schedule was somewhat less aggressive and I did hand buff so perhaps I will be ok. I was fortunate enough to take a French polishing class recently and that will likely be the method I use for applying Royal Lac in the future.

_________________
Steve Smith
"Music is what feelings sound like"

So, I just edited to subject of the thread and included a note in my original post noting that it was likely my technique that caused the crazing. I'd hate for this to have a negative impact of Vijay's business if there isn't an issue with product. He's been really great about all this even offering to walk me through the finishing process once I'm ready.

I plan to continue using Royal Lac. I'm real happy with it so far however, if I spray it again, I'll certainly modify my finish schedule.

_________________
Steve Smith
"Music is what feelings sound like"

Last weekend, I heard from a luthier who has used Royal-Lac in the past and was very happy with it. Unfortunately with the last instrument, he found crazing about a month after buffing. This incident prompted me to log onto the forum and see if others have had similar experiences. And I found this thread. First of all many thanks to Mike Waszazak for posting the email between him and myself. Transparency helps us all!
Anyways back to the luthier - On questioning I found that he only waited 2 weeks before wet sand leveling and buffing. Exposing a finish that is under cure to water and heat, generated during buffing, will cause failure. With a total of 4 Royal-Lac failures that have been recorded, all have two common problem sources - Water and Heat.
This prompts me to ask all you experts; Is wet sanding in between coats really necessary or is it just a habit that we, including myself, have formed and executed without much thought behind it? I believe so and correct me if you think otherwise. Let me explain..
The goal is to build up a finish of a certain thickness with coats that are free from drips or other blatantly visible defects. After cure, it is level wet sanded from 600 to 8000 grit to get a smooth flat surface and ready for buffing. So theoretically speaking, is in between wet sanding really required?? A light dry sand should be more than adequate, isn't it?
On the other hand if you look at the cross sectional view of the coats - it is true that the first coat is not totally flat but has undulations through out. Each successive coat will follow this undulated surface to a large extent. Hence, the end result is that the cross sectional topology of the total film is close enough to the first coat. After cure, undulations reduce due to self leveling as the solvent leaves the system. And lastly it is wet level sanded to 8000 grit to produce a flat surface for buffing. After sanding if the cross sectional topology is viewed again, it is actually a film with minor undulations that are directly proportional to a 8000 grit scratch pattern. My point being that eventually a film is produced that has the same density through out.

To sum it up, it leads me to believe that, whatever be the method of application, as long as the build up is good, the end result after buffing should be more than acceptable. This thought is only for luthiers who buff the surface for a high shine. Woodworkers finishing furniture is a different matter.
Please share your thoughts. I would love to hear from you all.
Vijay

With reference to Post by David Farmer on Mon Apr 11, 2016 5:21 pm:
I fully and totally agree with David. I have seen this happen with pure shellac too. I am supporting David so vociferously because a lot of folks think that pure shellac being so flexible, can withstand heavy coat after coat application.
Vijay

Hi Vijay,

I was just doing setup on a guitar that I sprayed with Royal Lac (one of two - more on the other one in a bit). This first guitar has also crazed much like in Mike's photos above. I only wet sand at the very end of the finish process and, in this case, 2 months after finishing so I don't have that as a potential issue. This guitar was buffed with a machine.

The second guitar has also crazed but to a much lesser degree. This guitar is still in the drying cabinet after about 4 months and has not been wet sanded or buffed. However I am guilty of spraying multiple coats at short intervals. Here is the schedule from my log that was used for both of these guitars.

Sand to 320 then 2 coats of Seal Lac at 20 min interval.
Wait 1 day. Scuff with 400 then 3 coats Royal Lac at 20 min intervals.
Wait 5 days. Scuff with 400 then 4 coats RL at 20 min intervals.
Wait 2 days. Scuff with 400 then 5 coats RL at 20 min intervals.
Wait 2 weeks. Level to about the 80% point with 400 dry. 4 coats RL thinned with 20% Everclear at 20 min intervals.
Wait 2 months. Level with 1000 grit wet and machine buff.

I measured the finish thickness at 0.006".

Based on Mike's schedule and your comments I think the big culprit is spraying too many coats too quickly. I appreciate you taking an interest in this discussion. It's very valuable to be able to to work together like this. My next attempt with Royal Lac will be French polished.

I share this in the hope that it will be helpful to some because this is a very nice looking finish.

_________________
Steve Smith
"Music is what feelings sound like"

Hi Steve,
Very sorry to hear about this development.
As you mention, it is the 20 minute interval that is the cause. Several points to keep in mind:
1) Spraying a 2 lb cut finish is a lot of solids at one time. About 20-21% solids by weight.
2) Spraying can be light or heavy. Everyone sprays differently.
3) Even though after 20 minutes it feels dry, it is still wet under that thin upper skin.
4) Even a 2lb cut of pure shellac flakes will craze when sprayed so quickly.
I spray no more than 3 coats a day with at least 3 hours in between. Many a times I limit it to 2 coats only.
If you French Polish or apply with a pad, a wet coat will instantly give you feedback by not letting the pad slide easily and/or observe some removal of the previous coat. This feedback mechanism is not available to a finisher who is spraying.
Royal-Lac is not a catalyzed finish. It is dependent on evaporation. Evaporation is directly related to the ambient conditions. Hence going slow while spraying will always help.
Hope this helps.

Hi Vejay, Thanks for the reply. Looks like the crazing is my fault for spraying too many coats too quickly, as I suspected. If I spray again I will follow your recommendation of no more than 3 coats a day with a minimum of 3 hours between coats.

_________________
Steve Smith
"Music is what feelings sound like"

Just have to say a special thanks to Vijay. He emailed me and is going to send me another quart of Royal Lac to use on my next finishing job. He's doing even knowing that I didn't apply the finish correctly. Thanks Vijay!!

_________________
Steve Smith
"Music is what feelings sound like"

You are welcome Steve.
On the subject of crazing, here is something interesting and related to coats in quick succession. A bit of background:
I got some wall paper installed in our home and the installer mentioned that there is no coating that resists color fade over time due to UV. So I decided to try shellac. I made a 2lb cut pure shellac solution in water. I couldn't use alcohol as a solvent since it would cause the colors to run.
I applied a coat with a foam brush and then applied another after 20 minutes. A week later I noticed the crazing.

Very interesting, I hadn't even known water could be used as a solvent for shellac,
Mike

Here is the method:
Completely dissolve 10 parts Borax in 100 parts warm distilled water. Borax can be substituted with plain ammonia too.
Add 25 parts of ground shellac flakes to mixture and insert container in a double boiler. Hide glue pot filled with water also works well. 25 parts will yield a 2 lb cut.
Swirl mixture time to time till dissolved.
Dissolution takes some time and plenty of swirling unlike alcohol dissolution.
The main problem with water based shellac is its tendency to exhibit voids due to surface tension of water.
To reduce this effect, instead of using 100 parts water, use 10 parts denatured alcohol and 90 parts water.
If above is applied with a brush, at least 2 hours in between coats at about 50% humidity is required to avoid crazing.

Mike, Vijay, everyone,

I haven't been keeping up with the forum and just noticed this set of posts.

I, too have had similar issues with spraying Royallac. Per my conversations with Vijay we determined that it was most likely due to wet sanding between straying coats of RL. OTOH, the guitars that I french polished are NOT crazing (no wet sanding) and look beautiful. Introducing water during the application process is the enemy to RL.

I would also like to commend Vijay for his willingness to support me in figuring out what I had done incorrectly. He is a real gem and those are difficult to find in any business, let alone the world of finish products. So thank you Vijay for your help. I'll keep french polishing with RL.

Steve

Let me add spraying too many coats with too little time between them will also lead to problems. Next batch will be french polished. I also thank Vijay for all of the help he gave me to find out what was going on.

_________________
Steve Smith
"Music is what feelings sound like"