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Author Topic: Sand n seal overpainting.  (Read 2037 times)

rich_morris

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Sand n seal overpainting.
« on: May 26, 2020, 04:18:35 pm »

Hi All,


I've read through a number of posts now, and read opinions in all sorts of direction on paint and varnish finishes.


I am currently building an Aero-naut classic sport boat, and approaching the stage when I'll need to add some paint and varnish.


The upper hull is mohogany, and I intend to clear lacquer that .
The lower hull is birch ply, and I intend to paint white.


My plan was to put several costs of Deluxe materials Sand n Seal over all the outside surfaces.


Then use an acrylic paint on the lower half and clear acrylic lawyer over the upper half.


The sand n seal says it is ok with acrylic paints.


I was just contemplating using Halfords own paint and laquer.  I had originally planned on using some brush paints.


Are Halfords, or any other acrylic spray products going to cause me any problems, or should I look elsewhere for a trouble free painting and laquer. An 11 year old will be helping/doing, so I want something as simple as possible.


Thanks for any help, or advice.


Rich






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DaveM

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Re: Sand n seal overpainting.
« Reply #1 on: May 26, 2020, 04:41:15 pm »

Rich
I've not used Sand n Seal myself but I would imagine that it contains a fine powder medium to fill the grain of the wood. Most sanding sealers do. That being the case then I'd advise you strongly to test it out on a scrap bit of the mahogany before you use it on the model. It may spoil the finish by obscuring the wood grain. People who build natural-finished hulls tend to use a much-thinned clear varnish and apply multiple coats, sanding between each one. Laborious but very satisfying when you view the result.

Search the forum for anything containing the words 'Riva' or 'Aquarama' for further info.
DaveM
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rich_morris

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Re: Sand n seal overpainting.
« Reply #2 on: May 26, 2020, 04:49:52 pm »

Thanks Dave,


As it happens I've already applied sand n seal to the side mahogany skins.
The kit instructions suggested to seal them before gluing them, to prevent glue stains. It looks ok!
It made them curl up the wrong way for skinning the boat, but that's done with now...


Rich
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Colin Bishop

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Re: Sand n seal overpainting.
« Reply #3 on: May 26, 2020, 06:38:34 pm »

I have been using Sand & Seal and it does dry pretty transparent.  I have just tried some on mahogany sheet and it seems to act very similar to acrylic quick dry matt varnish so I think you will be OK.

Having sealed the hull with Sand & Seal I would be in inclined to carry on with Ronseal Poylurethane varnish which seems to cover just about anything without reacting to it.

https://www.ronseal.com/for-home/wood-care/wood-varnish/ultra-tough-hardglaze-varnish/

Rustins also do something similar:

https://www.rustins.ltd/rustins/our-products/indoor/polyurethane-clear-varnish

Make sure you use the polyurethane type and not the quick dry.

All should be well then!

Colin

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Martin (Admin)

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Re: Sand n seal overpainting.
« Reply #4 on: May 27, 2020, 04:02:36 am »


Hey Colin!

Your link seems to be for the "interior", 'Ultra Tough Hardglaze Varnish'...


Links to the exterior Varnishes:

Crystal Clear Outdoor Varnish - https://www.ronseal.com/for-home/doors-windows/exterior-wood-varnish/

    All the protection you need without the colour
    A clear finish to let natural wood shine through
    Rainproof in one hour so no need to worry about downpours
    Doesn’t yellow like traditional varnishes

Yacht varnish - https://www.ronseal.com/for-home/doors-windows/yacht-varnish/

    Long lasting protection for outdoor wood
    Waterproof and protects from the sun
    Extremely tough – resists cracking, peeling and blistering
    Highlights wood’s natural colour
    Prevents wood from greying over time



Same for the Rustins:


Quick Dry Outdoor Clear Varnish
- https://www.ronseal.com/for-home/doors-windows/yacht-varnish/
 

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Colin Bishop

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Re: Sand n seal overpainting.
« Reply #5 on: May 27, 2020, 09:19:35 am »

Hey Martin!

The ones I listed were intentional!

The interior polyurethane varnishes are fine for models unless you leave them outdoors in all weathers or on a sunny windo sill. The polyurethane exterior ones have UV inhibitors in them which give them a yellowish tint - OK over bare wood but not good over light paint colours, especially white.

Yacht varnish is intended for above decks wood and not hulls although it is probably OK for models which don't spend much time in the water.

The Crystal Clear varnish is acrylic fast dry and not polyurethane. I find this type of varish doesn't always like being immersed, I and others have found that it can develop a milky bloom if in the water (as opposed to being just rained on). It also doesn't attach well to some surfaces and used over paint it can peel off in a thin film.

For modelling purposes the interior polyurethane is pretty much bomb proof and will go on over almost anything without reacting with it.

Colin
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DaveM

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Re: Sand n seal overpainting.
« Reply #6 on: May 27, 2020, 09:41:28 am »

I was recommended the Ronseal Ultra-Tough satin clear by Paul Freshney. Paul was editor of Model Boats magazine a few years ago and he makes superb scale models, mainly of military types. He suggested I thin it down 1:4 with white spirit for airbrushing - yes, that's four parts thinners to one part varnish. I've just finished painting the model I'm currently making and I have to say that it gives an excellent finish over Humrol Satin enamel.
DaveM
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rich_morris

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Re: Sand n seal overpainting.
« Reply #7 on: May 27, 2020, 11:09:05 am »

Hi,


Thanks for the recommendations.


I will be using either brush, or spray cans. I cannot justify an airbrush set up at this time.
Actually, to be correct, my 11 year old son will be using brush or spray cans, so the application needs to be quite fool proof.


I assumed the Halfords spray acrylic would be relatively UV stable and waterproof, given they will be used on a car, sat outside in all weathers?


Are the ronseal polyurethane products easy  to apply over white acrylic paints?


Thanks


Rich

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DaveM

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Re: Sand n seal overpainting.
« Reply #8 on: May 27, 2020, 11:54:56 am »

Are the ronseal polyurethane products easy  to apply over white acrylic paints?
As I've only ever applied them by spraying I can't say whether or not they brush well. The time-honoured piece of advice is to practice on a scrap panel first. The other advice is to use several thinned coats rather than one straight out of the tin. You need to be able to get the whole panel wet at the same time and work quickly or you'll likely end up with drag marks where you run one brushful into the last one. O - and avoid turpentine as a thinner - white spirit is much better and a lot cheaper!

I've had good reports of this compressor BTW. They also sell relatively inexpensive airbrushes and touch-up guns. https://bartsharpairbrush.co.uk/product/bartsharp-airbrush-compressor-tc90/
DaveM
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Colin Bishop

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Re: Sand n seal overpainting.
« Reply #9 on: May 27, 2020, 12:16:17 pm »

The Ronseal polyurethane should go on over acrylic paints OK as long as they are fully cured. However, anything that goes on over white will have some effect on appearance because you are adding a transparent layer which affects the reflective index of th surface. If at all possible it is best to use just the white paint. Many people, including me, use Halfords Appliance White spray which is a very pure white. It will need white primer under it and some people don't like that but I have found it OK if you use thin coats and allow to fully dry.

As Dave says, try out test pieces before you use your chosen combination on your boat, a very real case of a stitch in time saves nine.

Colin
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Martin (Admin)

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Re: Sand n seal overpainting.
« Reply #10 on: May 27, 2020, 01:01:31 pm »

Hey Martin!

The ones I listed were intentional! .....................

Colin


Ah, yes, thanks Colin..... I seem to remember having this conversation before .... now!  :embarrassed:


Ultra Tough Hardglaze VarnishDescription Wood that’s used a lot needs a lot of protection. Not only does this varnish protect against everyday knocks and scrapes, but it’s tough against chemicals, water and heat too. Long lasting protection with a clear and natural finish.
https://www.ronseal.com/for-home/wood-care/wood-varnish/ultra-tough-hardglaze-varnish/ 
Ronseal_UT_packshot.png   
 
--------------------------------------------------------------------------------------------------------

RUSTINS  - Indoor Wood FinishesPolyurethane Clear Varnish Clear varnish in gloss, satin and matt finishes. A tough and durable finish for all woodwork and cork. Apply 2-3 coats for the perfect finish. Re-coating time 2-8 hours. Can also be applied over Rustins Wood Dyes.
Features
For interior use
  • Gloss, satin & matt
  • Tough & durable
  • For all wood & cork
 
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rich_morris

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Re: Sand n seal overpainting.
« Reply #11 on: May 31, 2020, 10:26:59 am »

Hi all,


Well I think that the painting skills of my son may have more of an influence here than I thought.
Having just seen him using a paint brush, I'm not sure he'll get good results with a brush on laquer.
So my plan is spray cans.

I tried an old can of Rustoleum Painters Touch "enamel" acrylic spray, crystal clear over sand n seal. It didn't seem to react, and gets a reasonable gloss finish. It says it's exterior capable.

He painted the wooden dash panel with this, and I think we are happy he can get a nice result this way.
So, my plan is either:-

Rustoleum acrylics
Halfords car acrylic
Tamiya spray acrylics (TS type)

A white colour for the lower half, and a clear coat all over.
Are any of these likely to perform better long term? Waterproofness?

Thanks
 Rich

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