Blotchy Finish with sanding sealer/lacquer

[willbat]

Hi everyone

I have been spraying up some joint stools tonight and have come across a reoccurring problem, so I thought I would eventually find out what the problem is!

I have been spraying for a number of years now and after quite a bit of practice perfected a technique. One thing that still flaws a good finish is a blotchy finish that sporadically appears on a piece. I use cellulose based products when spraying and always start with a couple of coats of sanding sealer. The problem almost looks like it is some sort of waxy film on the surface and the lacquer is being shed away in certain spots. I have tried rubbing down between coats, firstly with appropriate finishing paper and then wiping with white spirit, but this does not always solve the problem. I am very careful not to transfer dirt onto the surface with my hands, so I am puzzled to why it still happens, it happens on all types of wood as well; could it be the spray gun or the sealer/lacquer itself?

The piece i am working on at the moment has a spirit based stain on the wood so cleaning the surface prior to spraying was difficult, the result was one of the worst cases of the blotchy patten happening and had to rub the piece back, which was very annoying, so any insight would be of great interest and very much appreciated.

Thanks

Will

 

[toolsntat]

Could be silicone if used in the manufacturing process...
The same stuff in cleaning products if refinishing older stuff...
It used to look like orange peel :roll:

 

[aurrida]

i have problems with oily woods so i wipe down with acetone and leave to dry a few minutes. i find, with the exception of ebony and grenadill, it eliminates the problems caused by natural oils clouding the finish. similar problems can arise with moisture being trapped under finish. can only suggest cleaning down wood before any application.

 

[aurrida]

sorry didnt read post properly, if its got a stain would alcohol be better than a spirit?

 

[willbat]

Orange peel! yes thats a very good way of describing the problem. Suppose i could try alcohol based cleaner, that would be fine to use over a spirit based stain would it?

 

[Shrubby]

Possibly your finishing paper might be leaving some of the stearate (white stuff) on the piece ? A wipe with spirit or meths(ethanol) should help. Change the rag often to avoid redistributing the problem - good luck
Matt

 

[Terry Smart]

Suppose i could try alcohol based cleaner, that would be fine to use over a spirit based stain would it?

Probably not; you'd be better off wiping the wood down before applying the stain.

I've also known people use Surgical Spirit for this problem with success.

 

[Limpet]

As you are spraying and finishing with cellulose then you could do worse than give Behlen Vinyl Sealer a try.

link