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Old 01-28-2011, 11:48 AM
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Re: Masonite / tempered hardboard question

Tempered and untempered hardboard are both quite suited as supports. Both are made using the same process. And technically, both are tempered, in that there is a heated curing and polishing process involved. The difference between the two comes at the end. "Tempered" hard bard has a minute amount of oil spread over the finished board and it is flashed off with heat. The oil acts as a catalyst, making the outer surface harder and less prone to warpage. The oil typically used since the 1950s anyway was linseed oil, although many manufactures now list a silicone based oil on the msds'.

The fear of "tempered" hardboard is based on an antiquated process, when a slow heat cure was used instead of a flashing off the oil and a great deal more oil was applied to the surface. And as I recall, the original process used a petroleum based oil. The slow cure method did often leave a slick oil residue, which was fine with oil based paints, but resins based paints and marine paints would have bonding issues.

The bigger concerns with hardboard is the process underwhich is it made, and the type of wood used. Tannins and acids from the latter can eventually cause discoloration of any paint application. That is why priming is so very vital. Hardboard is manufactured either by wet process, wet-dry process, or dry process.

Wet process uses a slurry of wood fiber and adhesive. This slurry is pressed between a plate and a mesh. This creates the ever famous smooth side and screen patterned side. Most hardboard is still prepared in this fashion. Wet-dry approach starts the same, but the slurry has a percentage of the water removed, either by centrifugation or by a dryer. The resulting pulp mixture is then pressed between two plates. This creates either two smooth sides, or smooth and laid texture sides. Dry process uses dry pulp and wood chips and uses resins to press into boards with either rough or smooth sides (ex chipboard, MDF). Dry process boards are softer and more prone to warping, and separating.

Just a note. Ampersand, who makes prepared hardboard supports, uses wet-dry process tempered hardboard for their products. The tempered board maintains a better with the primers and is more warp resistant.

Andrew
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Old 01-28-2011, 10:04 PM
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Re: Masonite / tempered hardboard question

Golden makes a GAC product that will prevent what they refer to as 'support induced discoloration', which means that tannins from certain kinds of wood pulp used to make hardboard can leach through the usual kinds of acrylic primers, and discolor the primer, AND your paint. possibly.
just to make things even more complicated:
i used masonite/hardboard for a while, cradled and uncradled, and had several problems with the hardboard delaminating, or peeling of layers.
since i started having my cradled panels made with 1/8" or 1/4" MDF (medium density fibreboard), i haven't had that problem, since it doesn't appear to be constructed from layers, but relatively amorphous, stable and doesn't bleed color into my primer. like hardboard, it can be prone to chipping at edges and corners in handling and transit.
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Old 02-02-2011, 05:38 PM
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Re: Masonite / tempered hardboard question

Andrew is accurate in his description of Hardboard/Masonite characteristics. This article says it all.

http://www.panel.com/uploads/whatisitcda0.pdf

I prefer tempered hardboard/masonite and have used it for over 41 years. It doesn't warp like some of the untempered I've used. I lightly sand it with a fine sandpaper and apply just white Acrylic Gesso, 3-4 coats, drying between coats.

I don't like to tint my gesso, as I find the white does a better job of reflecting the colors applied over it. Tinting tends to dull the type of artwork I like to do. Since I don't usually work larger than 4 foot, I cut my Masonite into 2-4 pieces and gesso it all first, so I can cut them at my liesure with a Table saw or even a cheap hand saw. I found it takes much more time to gesso them seperately than to cut them afterward.

I work with 1/8" all the way up to 4 foot lengths. I never had a warping problem as long as it's stored properly, so it can't bend.

BenS brings up a valid point too. I've had the Gesso discolor over time likely from bleeding through. Fortunately for me the Bleeding effect on my finished Oil Painting was unnoticeable in my case, even decades later.

I Hope all these responses are answering your questions.
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Old 02-05-2011, 09:35 AM
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Re: Masonite / tempered hardboard question

Thanks ddattler:
I especially like the idea of applying the gesso prior to the cutting.
That makes so much sense... duh!!
I began my first painting on a masonite panel and I'm noticing "score" lines where I guess I didn't sand properly. I was thinking that if I sanded too much I wouldn't establish any "tooth" to the surface.
I applied 2 coats of toned gesso and sanded lightly with 150 grit after each coat. Should I dilute the gesso so it doesn't go on so thickly or should I be more aggressive with my sanding. I do not like these "score" lines.
Thanks
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Old 02-07-2011, 03:11 PM
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Quote:
Originally Posted by ddattler
BenS brings up a valid point too. I've had the Gesso discolor over time likely from bleeding through. Fortunately for me the Bleeding effect on my finished Oil Painting was unnoticeable in my case, even decades later.
Important point this, glad you posted. It's quite obvious that SID is not exactly an everyday occurrence to begin with and on top of that it is either mostly or completely an issue only when painting with water-borne paint.

It is best to prep in a way that prevents it, but for many people this is just not necessary.


Quote:
Originally Posted by RaphaelG1
I began my first painting on a masonite panel and I'm noticing "score" lines where I guess I didn't sand properly.
Brushmarks in the primer? Or is it underneath, swirl marks from sanding or linear marks from the cutting?

Quote:
Originally Posted by RaphaelG1
I was thinking that if I sanded too much I wouldn't establish any "tooth" to the surface.
Only a small amount of sanding or scuffing (you can use Scotchbrite or nylon scrubbie pads instead of abrasive paper) is required to help promote tooth, more than that can be a problem in itself according to some sources as it takes away too much of the surface of the hardboard.

Quote:
Originally Posted by RaphaelG1
Should I dilute the gesso so it doesn't go on so thickly or should I be more aggressive with my sanding.
You can, but then you should apply more coats - the total thickness of primer is what's important at the end of the day, not the number of coats.

I personally never sand between coats any more as it's basically just wasteful of primer and time.

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Old 02-08-2011, 09:15 AM
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Re: Masonite / tempered hardboard question

Einion and others.. you've been way too kind with your help on this and I hate to impose further but I'm having an issue with what I'm calling "coverage." Unless the paint is very thickly applied it (the paint) seems to "slide around." Do you know what I mean? And none but the softest of my brushes seem to work. A brush with any "spring" has no chance of applying the paint to the surface.... the paint just gets pushed along. I'm either doing something wrong or masonite and I are heading for the divorce court.
I use W&N's water soluble paints that are not over-diluted with water or linseed oil (at least I don't think I'm over diluting).
Anyway Thanks.
Best
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Old 02-08-2011, 10:54 AM
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Re: Masonite / tempered hardboard question

Quote:
Originally Posted by RaphaelG1
Einion and others.. you've been way too kind with your help on this and I hate to impose further but I'm having an issue with what I'm calling "coverage." Unless the paint is very thickly applied it (the paint) seems to "slide around." Do you know what I mean? And none but the softest of my brushes seem to work. A brush with any "spring" has no chance of applying the paint to the surface.... the paint just gets pushed along. I'm either doing something wrong or masonite and I are heading for the divorce court.
I use W&N's water soluble paints that are not over-diluted with water or linseed oil (at least I don't think I'm over diluting).
Anyway Thanks.
Best

There can be several reasons for behavior in the paint. I will go through the most likely candidates.

First is the "gesso". Some acrylic gesso, has far more medium than pigment and grit. And so once dry, the finished surface lacks the expected tooth, and the paint will slide around more than on a better quality acrylic gesso surface. This is easily rectified by they use of very fine sandpaper, followed by a damp cloth to remove the dust. If you are using a traditional gesso, then up your dry component a bit and give it more bite.

Second is the paints. I am not familiar with water miscible oils, but typically speaking, the longer your paint (more medium) the slicker the stroke will be, and the shorter (less medium) the thicker and more sticky the paint will be. It is also true, that paints that have started to cure, from being out on the palette, can also lack cohesion, and slide about more on the surface. The latter can easily be fixed by adding in a touch of medium to reactivate the carrier, if it isn't too far gone.

There are other factors like contamination, with something leaving a residue, or the gesso/primer not quite set, and such of that nature, but those are increasingly unlikely.

Andrew
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Old 02-08-2011, 01:55 PM
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Re: Masonite / tempered hardboard question

Quote:
Originally Posted by Andrew
First is the "gesso". Some acrylic gesso, has far more medium than pigment and grit. And so once dry, the finished surface lacks the expected tooth, and the paint will slide around more than on a better quality acrylic gesso surface. This is easily rectified by they use of very fine sandpaper, followed by a damp cloth to remove the dust. If you are using a traditional gesso, then up your dry component a bit and give it more bite.


I guess this is as good a place to ask as any, but regardless of the surface the gesso is being applied to, when it comes to sand paper, how fine is fine? What grit?
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Old 02-08-2011, 02:19 PM
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Re: Masonite / tempered hardboard question

Quote:
Unless the paint is very thickly applied it (the paint) seems to "slide around." Do you know what I mean? And none but the softest of my brushes seem to work. A brush with any "spring" has no chance of applying the paint to the surface.... the paint just gets pushed along. I'm either doing something wrong or masonite and I are heading for the divorce court.

I appreciate nice, flat, minimum-textured surfaces upon which to do my glazing. This is one reason that I don't use stiff, natural bristle brushes. Hog bristle brushes tend to "plow up" as much paint as they apply, and I don't use them, for that reason. This "pushing along of the paint" is to be expected, though, when painting on a smooth surface, and it occurs quite routinely. The solution is to apply several layers of paint (image paint) instead of expecting one coat to "cover". If you are applying the paint correctly for glazing (thinly), it won't cover, nor can it be expected to do so.

I do avoid the stiff, natural bristles, though, and I use Taklon bristle brushes. They are soft, but have enough spring to apply the paint, but not enough to plow it back up when it is being applied.

Quote:
I guess this is as good a place to ask as any, but regardless of the surface the gesso is being applied to, when it comes to sand paper, how fine is fine? What grit?

For sanding acrylic gesso (primer), I use 150-grit, 3M Maroon Sandblaster paper. It stays open, and it is engineered to be used for latex and acrylic paints, without clogging. The advertising is correct--it does remain open. Finer grits (such as 300 and 600 grits) tend to do more "polishing" of the surface, and don't create nearly enough tooth for proper adherence of the oil paint. 150-grit may seem like a very coarse grit, but it isn't really very coarse, for practical, effective sanding.
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Old 02-08-2011, 02:52 PM
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Re: Masonite / tempered hardboard question

Thanks William.

I hear the term 'fine' sandpaper thrown around a lot, but never clearly defined. I had a mixed pack of coarse, medium and fine aluminum oxide sandpaper in my shed, and the 'fine' was 120. I was really curious how fine to go and still have some 'tooth'. I will check out the 3M Maroon paper.

And would this grit work equally well for both gesso on panel and canvas? I am planning on putting canvas on my panels, and also like to add an extra coat or two of gesso to some pre-primed and/or pre-stretched canvasses.
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Old 02-08-2011, 02:54 PM
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Quote:
Originally Posted by mtpalms
I guess this is as good a place to ask as any, but regardless of the surface the gesso is being applied to, when it comes to sand paper, how fine is fine? What grit?
Depends a bit on paper type and whether you use it wet or dry. The medium you're working in is also important - you can paint on a much smoother 'gesso' surface with acrylic or tempera than you should with oil paint.

Generally I'd suggest using between about 100 and 180 grit if painting in oils, so 150 is a good average; for acrylics I've gone up as high as P800 for prepping panels but I don't bother going that fine any more, just not necessary for the surface to be that smooth for the way I paint.

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Old 02-08-2011, 04:00 PM
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Re: Masonite / tempered hardboard question

Thanks Einion. I paint exclusively in oils, and it's always nice when opinions agree, ie 150 grit.

I guess I assumed the sanding would be dry, at least when prepping for oils.
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Old 02-08-2011, 04:18 PM
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Re: Masonite / tempered hardboard question

Quote:
Originally Posted by mtpalms
Thanks William.

I hear the term 'fine' sandpaper thrown around a lot, but never clearly defined. I had a mixed pack of coarse, medium and fine aluminum oxide sandpaper in my shed, and the 'fine' was 120. I was really curious how fine to go and still have some 'tooth'. I will check out the 3M Maroon paper.

And would this grit work equally well for both gesso on panel and canvas? I am planning on putting canvas on my panels, and also like to add an extra coat or two of gesso to some pre-primed and/or pre-stretched canvasses.

I believe it would be as appropriate for sanding either canvas or panels. Just do not be tempted to use a sanding block for sanding canvases. That would work on non-flexible surface such as a panel, but would not be as good for sanding a flexible canvas. For that, I would use my fingers backing up the sandpaper for doing the sanding.
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Old 02-09-2011, 01:27 PM
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Re: Masonite / tempered hardboard question

I like to thin my gesso with just enough water to smooth the texture when applying it. I buy my Gesso by the gallon, so I keep extra jars or seal-able containers for storing the mixed gesso. Don't over thin it, or you'll have to put on allot more coats. I can't tell you how much to thin your' particular gesso since every gesso has it's own characteristics. I currently use Dickblick's studio grade gesso, and mix it 1 part water to 6-8 parts gesso. You may want to find a Gesso you like and stick with it since every gesso reacts slightly diffferently to mixing, sanding and painting.

Last time, I applied it with a medium nap 3 inch paint roller to create a more consistent texture, requiring less sanding later. I allow it to dry about 1/2 hour at room temperature, between coats, dry to the touch, but still fresh enough to adhere to the next coat of gesso without sanding (don't over-work the gesso between coats unless they dry completely, or I've found it tends to pull the previous coat away from the board).

Dry sand the final coat after it dries at least overnight or just prior to painting on it. I sand it enough to give the paints a surface to stick to, but enough to get the finish I want. Yes, 150 grit sand papers are good grades. Anything coarser can strip or scratch the gesso right off of your masonite/hardboard. If you have an orbital sander, it saves allot of time if you are using hardboard. Just be careful not to over-sand it.
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Last edited by ddattler : 02-09-2011 at 01:46 PM.
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Old 02-09-2011, 02:24 PM
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Re: Masonite / tempered hardboard question

Thanks for the application and sanding tips, ddattler.

In fact, I just placed an order for Blick's studio grade gesso. Now that I am armed with all of this information, I may go ahead and try painting on a few gesso'd panels as well as some with canvas on them.

This has been a great thread, thanks everybody!
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