# Slightly rough after spray painting



## Matthewt1970 (Sep 16, 2008)

I am not a furniture finish expert, but I think your final sanding needs to be with a 600 grit or buffing pad.


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## colinmc8 (Jun 6, 2010)

Thanks Matthew, basically the question is, is it normal practice to sand after the final coat is applied or is it normally left as is? Oh and I'm currently doing a painted gloss finish, solvent based.


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## Rcon (Nov 20, 2009)

colinmc8 said:


> Thanks Matthew, basically the question is, is it normal practice to sand after the final coat is applied or is it normally left as is? Oh and I'm currently doing a painted gloss finish, solvent based.


Using a compressed air sprayer? I'd guess that your product is drying in the air before it hits the surface - you need a retarder. Can't suggest one though as I don't know what product you're using.


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## colinmc8 (Jun 6, 2010)

Thanks for your reply, I have never heard of retarder before, just done some reading in the subject. I do need to thin the paint quite alot for it to come out the gun smoothly. Does thinning the paint cause it to dry faster in the air? or is there any other way to prevent this, I would prefer not to have to buy more products.


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## mark942 (Feb 2, 2008)

Over thinning paint will cause you problems. Do you have the right needle for your particular application? When you say solvent based material, do you mean Naptha, Lacquer, MEK, etc? What ratio mix are you using? What grit paper are you using between coats? Do you size up grit between coats? 


Yes, sanding between coats is necessary. :thumbsup:


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## colinmc8 (Jun 6, 2010)

Hi mark,

All of the questions you just asked are the reason I joined a forum lol I don't really know is the quick answer!
Lets see I'm using gloss paint and thinning it down with mineral spirits, I don't do exact measurments for the mix...maybe I should? probably about 1 part mineral spirit to 2 part paint.
The needle is 1.4 (Thats stamped on it. I don't know if that helps)
Between coats I use a sanding sponge I guess its around 240+ grit.
Just one quick question, after the last coat, do you normally just leave it or give it a very light sanding or something else?
Thanks.


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## mark942 (Feb 2, 2008)

http://www.advmachinery.com/c-40-7500-series-needles-nozzles-chart.aspx


I copied this for you to look at. Reinforces the reducer comment.
*Is thinning necessary or important with HVLP?*  Viscosity of coatings is important. Although we supply a guide, there is often some trial and error involved in arriving at the best viscosity. If a product is thinned too much, there are runs. Too thick and 'orange peel' or rough finish is the result. When thinning, it is essential to use a reducer that is compatible with the product you are using. To be sure, buy a thinner/solvent made by the same coatings company - always verify that it is the right product.   It is wise to experiment on a practice piece to ensure that the finish is perfect. You may also request information from the coatings manufacturer - don't forget to mention you are spraying with HVLP equipment.



Try starting with your 240 then move up to 1000, in some cases I have used 3200, the finer the grit the smaller the scratches it will leave. If it is a very very fine finish your looking to get, after sanding try using wax after all spraying is done. Then hand rub it to a glass finish.


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## colinmc8 (Jun 6, 2010)

Thanks alot, your help and time is much appreciated. In the end I just gave a light sanding after the last coat and it is fine. I will remember your advice for future projects.


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