Importance of putty in wood maintenance
One of the main problems in repairing or restoring an old one artifact in wood are the holes, crevices or cavity that are created on its surface due to various causes.
One of the most common defects are the shrinkage cracks, due to the seasoning not optimal wood or al abrupt change of the environmental conditions in which the artifact is kept, for example from a cool, humid and ventilated environment to a hot and very dry one.
Shrinkage cracks are normally not filled, except in some special cases such as window frames, blackout elements or table tops.
Slots for joining parts
Another common problem concerns the creation of crevices perfectly linear due to disunione of the singles boards, normally joined by joints, pins or wooden chocks, which form extensive artifacts and coplanar such as doors, window shutters, furniture doors or table tops.
In this case, after making sure that the wood has adapted perfectly to the environment in which it is located, to avoid futures boats O enlargements of the cracks, it is necessary to proceed with grouting to prevent water, dust and dirt can enter the cracks accelerating the degradation.
Flickering holes, breaks, rot and defects
In the case instead of flicker holes of xylophagous insects such as woodworms or termites, after the biocide treatment, grouting in a piece of furniture improves the aesthetics and prevents the accumulation of dust and dirt.
The last cases concern, finally, the real one break of parts with formation of fractures o net injuries and the need for rebuild parts also consistent because they are missing, marcescens or spontaneously detached due to defects such as knots O chives.
In these cases, a plug of suitable shape, essence and size is normally inserted in correspondence with the lack and then the remaining cracks are filled.
When to repair yourself
Of course for the more delicate interventions, especially if related to the latter category, it is necessary to contact a specialized restorer, while for the simpler grouting, if you have good dexterity, you can proceed independently.
Traditional plaster based on Bologna gypsum
There are numerous traditional recipes of putty for wood, each suitable for specific applications.
I materials necessary, already known and used for centuries for the creation, decoration and maintenance of furniture, statues or paintings on wood, are easily available in the paint shops more supplied, in the shops of articles for the fine Arts or in specialized sites such as Online Restoration O Belsito Antiquity.
Ingredients of plaster putty
A first recipe of stucco, especially suitable for furniture and gilded frames and the repair of small holes and cracks, is based on Bologna gypsum, mineral pigments and wood glue.
The plaster of Bologna, also used as a preparatory layer for the gilding, is a particular type of gypsum that does not harden in contact with water.
Also, if you work on non-gilded wooden furniture, you can to color the putty with i inorganic pigments, based on oxides and natural earths, also used in fresco or lime painting.
The wood glues most used in the restoration are instead:
- the with garavella O carpenter’s glue, obtained from the waste of the leather;
- the bone glue, obtained from the grinding of animals destined for slaughter;
- the rabbit glue, obtained from rabbit skin waste.
These glues are normally sold in slabs or pearls; to be used they must first be left to rest for a few hours in cold water and subsequently heated to water bath with a saucepan.
Preparation and application of the putty
To prepare the putty, on a hard plan and waterproof, for example of marble, Bologna gypsum is mixed with pigmentif necessary doing some evidence to find the right color and then add the previously prepared glue.
And amalgam then all until you get one pasty consistency, free of lumps and easy to apply with a spatula.
The proportions of ingredients vary according touse grout: in general for the parts most exposed to impacts such as edges it is necessary to increase the quantity of glue, vice versa it can be reduced to treat flat surfaces.
Before application it is advisable clean thoroughly the surfaces from all traces of sawdust, dust and dirt, and then apply a brush coat of shellac to prevent the formation of halos e irreversible stains.
The putty can be applied with one spatula, pressing lightly to avoid the formation of air bubbles and applying more material than strictly necessary, because a certain reduction in volume occurs during drying.
In case of holes or very large lesions, for an optimal result it is advisable to divide the work into several phases, leaving it to rest for a few hours after applying the filler.
At this point the excess material with a light sanding manual and then proceed to final treatments such as wax polishing or re-gilding.
It stucco a cera it is especially recommended for elements not exposed to shocks and can also be applied by a beginner, as completely reversible.
Ingredients and preparation of the wax putty
For the preparation it is sufficient to heat the virgin beeswax with a little bit of turpentine essence, add the pigment in the desired quantity, mix everything very well and pour the compound into one die (e.g. made of foil) to get a stick similar to a wax crayon.
Once hardened, the filler is ready.
In alternative you can buy colored wax putty in stick by Antichità Belsito, ready to use and available in one wide range of colors.
Application of the wax putty
As wax putty also tends to stain the wood, before the application it is necessary to proceed to a protective application shellac, similarly to what has already been seen for the plaster-based stucco of Bologna.
Putty applies detaching some material from the stick and working it with your fingers to get a kind of sausage gives to insert in the lesion or hole to be grouted, pressing well with a spatula to avoid the formation of air bubbles e seal well all the cracks.
Once the application is complete it waits for a few minutes and rubs it off excess putty with a woolen cloth.
Alternatively you can pass the stick of putty directly over the crack, just like a chalk or a coloured pencil, until the entire cavity is perfectly filled: this method is very effective for more superficial injuries.
Since shellac putty keeps a certain hardness even after drying, it is the only traditional putty also suitable for sealing holes and deep injuries or even replenish small gaps.
For very large holes, however, it is advisable to insert a wooden dowel, carefully filling the remaining cracks.
Ingredients and preparation of shellac putty
Exist various recipes to prepare shellac putty: the simplest one involves cera d’api, pigments and precisely the shellac, a natural secretion of an insect that lives in Thailand and in the Indian region of Assam.
It is sold in solid flakes.
To prepare the putty yes dissolve the wax and shellac in a water bath, adding the pigments and mixing the mixture, which again is then poured into one small mold O cast on a marble surface and then worked with your hands to get a stick.
Application of shellac filler
To apply the stucco, which is more complex than in the previous cases, one is needed spatula it’s a shaped spoon as a small spout.
This recipe is especially suitable for filling holes, lesions and cavities in horizontal surfaces, for example table tops or drawers: door e furniture doors they go therefore disassembled and placed horizontally.
First you have to protect the parts not to be treated with del Scotch tape that leaves no traces after its removal at the end of the work.
Then comes off a small piece of putty from the stick, put it in the spoon and heat it making it melt. At this point the mixture is poured into the hole to be grouted, working it with the heated spatula to correct the smudges.
Once the operation is completed e hardened putty, excess material is removed by lightly sanding.
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